@incollection{emenike_point_2019,
	title = {A point estimate method-based back-off approach to robust optimization: application to pharmaceutical processes},
	volume = {42},
	copyright = {All rights reserved},
	isbn = {978-0-12-819939-8},
	booktitle = {Computer {Aided} {Chemical} {Engineering}},
	author = {Emenike, Victor N. and Xie, Xiangzhong and Krewer, Ulrike and Schenkendorf, René},
	year = {2019},
	doi = {10.1016/B978-0-128-18634-3.50038-2},
	pages = {223--228},
}

@article{xie_robust_2019,
	title = {Robust optimization of a pharmaceutical freeze-drying process under non-{Gaussian} parameter uncertainties},
	copyright = {All rights reserved},
	issn = {00092509},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S0009250919305275},
	doi = {10.1016/j.ces.2019.06.023},
	language = {en},
	urldate = {2019-06-23},
	journal = {Chemical Engineering Science},
	author = {Xie, Xiangzhong and Schenkendorf, René},
	month = jun,
	year = {2019},
	pages = {S0009250919305275},
}

@article{schenkendorf_efficient_2019,
	title = {An efficient polynomial chaos expansion strategy for active fault identification of chemical processes},
	volume = {122},
	copyright = {All rights reserved},
	issn = {00981354},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S0098135418308652},
	doi = {10.1016/j.compchemeng.2018.08.022},
	language = {en},
	urldate = {2019-06-04},
	journal = {Computers \& Chemical Engineering},
	author = {Schenkendorf, René and Xie, Xiangzhong and Krewer, Ulrike},
	month = mar,
	year = {2019},
	pages = {228--237},
}

@article{xie_efficient_2019,
	title = {Efficient sensitivity analysis and interpretation of parameter correlations in chemical engineering},
	volume = {187},
	copyright = {All rights reserved},
	issn = {09518320},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S0951832018300541},
	doi = {10.1016/j.ress.2018.06.010},
	language = {en},
	urldate = {2019-06-04},
	journal = {Reliability Engineering \& System Safety},
	author = {Xie, Xiangzhong and Schenkendorf, René and Krewer, Ulrike},
	month = jul,
	year = {2019},
	pages = {159--173},
}

@article{laue_joint_2019,
	title = {Joint structural and electrochemical modeling: {Impact} of porosity on lithium-ion battery performance},
	copyright = {All rights reserved},
	issn = {00134686},
	shorttitle = {Joint structural and electrochemical modeling},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S0013468619309065},
	doi = {10.1016/j.electacta.2019.05.005},
	language = {en},
	urldate = {2019-05-18},
	journal = {Electrochimica Acta},
	author = {Laue, Vincent and Röder, Fridolin and Krewer, Ulrike},
	month = may,
	year = {2019},
	pages = {S0013468619309065},
}

@article{rohe_processes_2019,
	title = {Processes and their {Limitations} in {Oxygen} {Depolarized} {Cathodes}: {A} {Dynamic} {Model}‐{Based} {Analysis}},
	copyright = {All rights reserved},
	issn = {1864-5631, 1864-564X},
	shorttitle = {Processes and their {Limitations} in {Oxygen} {Depolarized} {Cathodes}},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/cssc.201900312},
	doi = {10.1002/cssc.201900312},
	language = {en},
	urldate = {2019-04-09},
	journal = {ChemSusChem},
	author = {Röhe, Maximilian and Kubannek, Fabian and Krewer, Ulrike},
	month = apr,
	year = {2019},
	pages = {cssc.201900312},
}

@article{frey_novel_2019,
	title = {Novel electrodynamic oscillation technique enables enhanced mass transfer and mixing for cultivation in micro‐bioreactor},
	copyright = {All rights reserved},
	issn = {8756-7938, 1520-6033},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/btpr.2827},
	doi = {10.1002/btpr.2827},
	language = {en},
	urldate = {2019-04-25},
	journal = {Biotechnology Progress},
	author = {Frey, Lasse Jannis and Vorländer, David and Rasch, Detlev and Ostsieker, Hendrik and Müller, Bernhard and Schulze, Moritz and Schenkendorf, René and Mayr, Torsten and Grosch, Jan‐Hendrik and Krull, Rainer},
	month = apr,
	year = {2019},
	pages = {e2827},
}

@article{wolff_understanding_2019,
	title = {Understanding nonlinearity in electrochemical systems},
	volume = {227},
	copyright = {All rights reserved},
	issn = {1951-6355, 1951-6401},
	url = {http://link.springer.com/10.1140/epjst/e2019-800135-2},
	doi = {10.1140/epjst/e2019-800135-2},
	language = {en},
	number = {18},
	urldate = {2019-04-13},
	journal = {The European Physical Journal Special Topics},
	author = {Wolff, Nicolas and Harting, Nina and Röder, Fridolin and Heinrich, Marco and Krewer, Ulrike},
	month = apr,
	year = {2019},
	pages = {2617--2640},
}

@article{haisch_quantification_2019,
	title = {Quantification of formaldehyde production during alkaline methanol electrooxidation},
	copyright = {All rights reserved},
	issn = {13882481},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S1388248119300773},
	doi = {10.1016/j.elecom.2019.03.013},
	language = {en},
	urldate = {2019-03-30},
	journal = {Electrochemistry Communications},
	author = {Haisch, Theresa and Kubannek, Fabian and Haisch, Christoph and Bahnemann, Detlef W. and Krewer, Ulrike},
	month = mar,
	year = {2019},
}

@article{roder_model_2019,
	title = {Model {Based} {Multiscale} {Analysis} of {Film} {Formation} in {Lithium}-{Ion} {Batteries}},
	copyright = {All rights reserved},
	issn = {25666223},
	url = {http://doi.wiley.com/10.1002/batt.201800107},
	doi = {10.1002/batt.201800107},
	language = {en},
	urldate = {2019-02-10},
	journal = {Batteries \& Supercaps},
	author = {Röder, Fridolin and Laue, Vincent and Krewer, Ulrike},
	month = feb,
	year = {2019},
}

@article{kadyk_design_2019,
	title = {Design of {Fuel} {Cell} {Systems} for {Aviation}: {Representative} {Mission} {Profiles} and {Sensitivity} {Analyses}},
	volume = {7},
	copyright = {All rights reserved},
	issn = {2296-598X},
	shorttitle = {Design of {Fuel} {Cell} {Systems} for {Aviation}},
	url = {https://www.frontiersin.org/article/10.3389/fenrg.2019.00035/full},
	doi = {10.3389/fenrg.2019.00035},
	urldate = {2019-04-09},
	journal = {Frontiers in Energy Research},
	author = {Kadyk, Thomas and Schenkendorf, René and Hawner, Sebastian and Yildiz, Bekir and Römer, Ulrich},
	month = apr,
	year = {2019},
	pages = {35},
}

@article{laue_modelbased_2019,
	title = {Model‐based {Uncertainty} {Quantification} for the {Product} {Properties} of {Lithium}‐{Ion} {Batteries}},
	copyright = {All rights reserved},
	issn = {2194-4288, 2194-4296},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/ente.201900201},
	doi = {10.1002/ente.201900201},
	language = {en},
	urldate = {2019-04-01},
	journal = {Energy Technology},
	author = {Laue, Vincent and Schmidt, Oke and Dreger, Henning and Xie, Xiangzhong and Röder, Fridolin and Schenkendorf, Rene and Kwade, Arno and Krewer, Ulrike},
	month = mar,
	year = {2019},
}

@article{heinrich_physico-chemical_2019,
	title = {Physico-chemical modeling of a {Lithium}-ion battery: {An} ageing study with {Electrochemical} {Impedance} {Spectroscopy}},
	copyright = {All rights reserved},
	issn = {25666223},
	shorttitle = {Physico-chemical modeling of a {Lithium}-ion battery},
	url = {http://doi.wiley.com/10.1002/batt.201900011},
	doi = {10.1002/batt.201900011},
	language = {en},
	urldate = {2019-03-09},
	journal = {Batteries \& Supercaps},
	author = {Heinrich, Marco and Wolff, Nicolas and Harting, Nina and Laue, Vincent and Röder, Fridolin and Seitz, Steffen and Krewer, Ulrike},
	month = mar,
	year = {2019},
}

@article{xie_effect_2019,
	title = {The {Effect} of {Correlated} {Kinetic} {Parameters} on ({Bio}){Chemical} {Reaction} {Networks}},
	copyright = {All rights reserved},
	issn = {0009286X},
	url = {http://doi.wiley.com/10.1002/cite.201800201},
	doi = {10.1002/cite.201800201},
	language = {en},
	urldate = {2019-02-27},
	journal = {Chemie Ingenieur Technik},
	author = {Xie, Xiangzhong and Schenkendorf, René and Krewer, Ulrike},
	month = feb,
	year = {2019},
}

@article{xie_stochastic_2019,
	title = {Stochastic back-off-based robust process design for continuous crystallization of ibuprofen},
	copyright = {All rights reserved},
	issn = {00981354},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S0098135418313085},
	doi = {10.1016/j.compchemeng.2019.02.009},
	language = {en},
	urldate = {2019-02-15},
	journal = {Computers \& Chemical Engineering},
	author = {Xie, Xiangzhong and Schenkendorf, René},
	month = feb,
	year = {2019},
}

@article{laue_modeling_2019,
	title = {Modeling the {Influence} of {Mixing} {Strategies} on {Micro} {Structural} {Properties} of {All}-{Solid} {State} {Electrodes}},
	copyright = {All rights reserved},
	issn = {21944288},
	url = {http://doi.wiley.com/10.1002/ente.201801049},
	doi = {10.1002/ente.201801049},
	language = {en},
	urldate = {2019-02-01},
	journal = {Energy Technology},
	author = {Laue, Vincent and Wolff, Nicolas and Röder, Fridolin and Krewer, Ulrike},
	month = jan,
	year = {2019},
}

@article{neumann_analyzing_2019,
	title = {Analyzing uncertainties in model response using the point estimate method: {Applications} from railway asset management},
	copyright = {All rights reserved},
	issn = {1748-006X, 1748-0078},
	shorttitle = {Analyzing uncertainties in model response using the point estimate method},
	url = {http://journals.sagepub.com/doi/10.1177/1748006X19825593},
	doi = {10.1177/1748006X19825593},
	language = {en},
	urldate = {2019-01-30},
	journal = {Proceedings of the Institution of Mechanical Engineers, Part O: Journal of Risk and Reliability},
	author = {Neumann, Thorsten and Dutschk, Beate and Schenkendorf, René},
	month = jan,
	year = {2019},
	pages = {1748006X1982559},
}

@article{harting_state--health_2019,
	title = {State-of-{Health} {Diagnosis} of {Lithium}-{Ion} {Batteries} {Using} {Nonlinear} {Frequency} {Response} {Analysis}},
	volume = {166},
	copyright = {All rights reserved},
	issn = {0013-4651, 1945-7111},
	url = {http://jes.ecsdl.org/lookup/doi/10.1149/2.1031902jes},
	doi = {10.1149/2.1031902jes},
	language = {en},
	number = {2},
	urldate = {2019-01-30},
	journal = {Journal of The Electrochemical Society},
	author = {Harting, Nina and Wolff, Nicolas and Röder, Fridolin and Krewer, Ulrike},
	year = {2019},
	pages = {A277--A285},
}

@article{emenike_robust_2019,
	title = {Robust dynamic optimization of enzyme-catalyzed carboligation: {A} point estimate-based back-off approach},
	volume = {121},
	copyright = {All rights reserved},
	issn = {00981354},
	shorttitle = {Robust dynamic optimization of enzyme-catalyzed carboligation},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S0098135418306689},
	doi = {10.1016/j.compchemeng.2018.10.006},
	language = {en},
	urldate = {2018-11-14},
	journal = {Computers \& Chemical Engineering},
	author = {Emenike, Victor N. and Xie, Xiangzhong and Schenkendorf, René and Spiess, Antje C. and Krewer, Ulrike},
	month = feb,
	year = {2019},
	pages = {232--247},
}

@article{schenkendorf_impact_2018,
	title = {The {Impact} of {Global} {Sensitivities} and {Design} {Measures} in {Model}-{Based} {Optimal} {Experimental} {Design}},
	volume = {6},
	copyright = {All rights reserved},
	issn = {2227-9717},
	url = {http://www.mdpi.com/2227-9717/6/4/27},
	doi = {10.3390/pr6040027},
	language = {en},
	number = {4},
	urldate = {2019-03-12},
	journal = {Processes},
	author = {Schenkendorf, René and Xie, Xiangzhong and Rehbein, Moritz and Scholl, Stephan and Krewer, Ulrike},
	month = mar,
	year = {2018},
	pages = {27},
}

@article{harting_identification_2018,
	title = {Identification of {Lithium} {Plating} in {Lithium}-{Ion} {Batteries} using {Nonlinear} {Frequency} {Response} {Analysis} ({NFRA})},
	volume = {281},
	copyright = {All rights reserved},
	issn = {00134686},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S0013468618311848},
	doi = {10.1016/j.electacta.2018.05.139},
	language = {en},
	urldate = {2018-12-11},
	journal = {Electrochimica Acta},
	author = {Harting, Nina and Wolff, Nicolas and Krewer, Ulrike},
	month = aug,
	year = {2018},
	pages = {378--385},
}

@article{wolff_nonlinear_2018,
	title = {Nonlinear frequency response analysis on lithium-ion batteries: {Process} identification and differences between transient and steady-state behavior},
	copyright = {All rights reserved},
	issn = {00134686},
	shorttitle = {Nonlinear frequency response analysis on lithium-ion batteries},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S0013468618328172},
	doi = {10.1016/j.electacta.2018.12.107},
	language = {en},
	urldate = {2019-01-02},
	journal = {Electrochimica Acta},
	author = {Wolff, Nicolas and Harting, Nina and Heinrich, Marco and Krewer, Ulrike},
	month = dec,
	year = {2018},
}

@inproceedings{clees_parameter_2018,
	address = {Porto, Portugal},
	title = {Parameter {Identification} in {Cyclic} {Voltammetry} of {Alkaline} {Methanol} {Oxidation}:},
	copyright = {All rights reserved},
	isbn = {978-989-758-323-0},
	shorttitle = {Parameter {Identification} in {Cyclic} {Voltammetry} of {Alkaline} {Methanol} {Oxidation}},
	url = {http://www.scitepress.org/DigitalLibrary/Link.aspx?doi=10.5220/0006832002790288},
	doi = {10.5220/0006832002790288},
	urldate = {2018-12-11},
	booktitle = {Proceedings of 8th {International} {Conference} on {Simulation} and {Modeling} {Methodologies}, {Technologies} and {Applications}},
	publisher = {SCITEPRESS - Science and Technology Publications},
	author = {Clees, Tanja and Nikitin, Igor and Nikitina, Lialia and Pott, Sabine and Krewer, Ulrike and Haisch, Theresa},
	year = {2018},
	pages = {279--288},
}

@article{thomitzek_simulating_2018,
	title = {Simulating {Process}-{Product} {Interdependencies} in {Battery} {Production} {Systems}},
	volume = {72},
	copyright = {All rights reserved},
	issn = {22128271},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S2212827118301586},
	doi = {10.1016/j.procir.2018.03.056},
	language = {en},
	urldate = {2018-12-11},
	journal = {Procedia CIRP},
	author = {Thomitzek, Matthias and Schmidt, Oke and Röder, Fridolin and Krewer, Ulrike and Herrmann, Christoph and Thiede, Sebastian},
	year = {2018},
	pages = {346--351},
}

@article{roder_direct_2018,
	title = {Direct {Coupling} of {Continuum} and {Kinetic} {Monte} {Carlo} {Models} for {Multiscale} {Simulation} of {Electrochemical} {Systems}},
	copyright = {All rights reserved},
	issn = {00981354},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S0098135418309013},
	doi = {10.1016/j.compchemeng.2018.12.016},
	language = {en},
	urldate = {2018-12-11},
	journal = {Computers \& Chemical Engineering},
	author = {Röder, Fridolin and Braatz, Richard D. and Krewer, Ulrike},
	month = dec,
	year = {2018},
}

@article{wolff_model_2018,
	title = {Model {Based} {Assessment} of {Performance} of {Lithium}-{Ion} {Batteries} {Using} {Single} {Ion} {Conducting} {Electrolytes}},
	volume = {284},
	copyright = {All rights reserved},
	issn = {00134686},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S001346861831630X},
	doi = {10.1016/j.electacta.2018.07.125},
	language = {en},
	urldate = {2018-12-11},
	journal = {Electrochimica Acta},
	author = {Wolff, Nicolas and Röder, Fridolin and Krewer, Ulrike},
	month = sep,
	year = {2018},
	pages = {639--646},
}

@article{abt_model-based_2018,
	title = {Model-based tools for optimal experiments in bioprocess engineering},
	volume = {22},
	copyright = {All rights reserved},
	issn = {22113398},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S221133981830056X},
	doi = {10.1016/j.coche.2018.11.007},
	language = {en},
	urldate = {2018-12-11},
	journal = {Current Opinion in Chemical Engineering},
	author = {Abt, Vinzenz and Barz, Tilman and Cruz, Nicolay and Herwig, Christoph and Kroll, Paul and Möller, Johannes and Pörtner, Ralf and Schenkendorf, René},
	month = dec,
	year = {2018},
	pages = {244--252},
}

@article{kubannek_concentration_2018,
	title = {Concentration {Pulse} {Method} for the {Investigation} of {Transformation} {Pathways} in a {Glycerol}-{Fed} {Bioelectrochemical} {System}},
	volume = {6},
	copyright = {All rights reserved},
	issn = {2296-598X},
	url = {https://www.frontiersin.org/article/10.3389/fenrg.2018.00125},
	doi = {10.3389/fenrg.2018.00125},
	abstract = {We investigated transformation pathways and determined rate constants in a continuously operated glycerol-fed bioelectrochemical system under chemostatic conditions by applying concentration pulses of various intermediates. Our methodology does not require the interruption of the continuous operation and is thus in principle suitable for elucidating processes in continuously operated bioreactors in industry as well as in laboratory studies. Specifically for the example of glycerol electrooxidation, pulse responses of current density and effluent concentrations reveal that glycerol is first fermented to acetate, which is then oxidized electrochemically by the anode respiring bacteria. Microbial community analysis confirms this division of labour with a bioanode dominated by Geobacter species 92.8 \%) and a much more diverse fermenting community in the planktonic phase, containing mainly Desulfovibrio sp. (45.2 \%) and Spiroaetales (18.1 \%). Desulfovibrio and Geobacter species are identified as promising candidates for tailored communities for glycerol electro-oxidation. From an acetate concentration pulse experiment, growth rates and half saturation rate constants for the biofilm of K\_S = 1.4 mol mˆ-3 and d(q\_max,Ac X\_bf)/dt = 933 mmol mˆ-2 dˆ-2 are obtained. Furthermore, 1,3-propanediol and glycerol concentration pulse experiments show that the reaction from glycerol to 1,3-propanediol is reversed at high 1,3-propanediol concentrations. The presented methodology allows one to study pathways and extract rate constants through simple experiments in a running system without irreversibly altering the microbial community or destroying the biofilm.},
	journal = {Frontiers in Energy Research},
	author = {Kubannek, Fabian and Moß, Christopher, Christopher and Huber, Katharina and Overmann, Jörg and Schröder, Uwe and Krewer, Ulrike},
	year = {2018},
	pages = {125},
}

We investigated transformation pathways and determined rate constants in a continuously operated glycerol-fed bioelectrochemical system under chemostatic conditions by applying concentration pulses of various intermediates. Our methodology does not require the interruption of the continuous operation and is thus in principle suitable for elucidating processes in continuously operated bioreactors in industry as well as in laboratory studies. Specifically for the example of glycerol electrooxidation, pulse responses of current density and effluent concentrations reveal that glycerol is first fermented to acetate, which is then oxidized electrochemically by the anode respiring bacteria. Microbial community analysis confirms this division of labour with a bioanode dominated by Geobacter species 92.8 %) and a much more diverse fermenting community in the planktonic phase, containing mainly Desulfovibrio sp. (45.2 %) and Spiroaetales (18.1 %). Desulfovibrio and Geobacter species are identified as promising candidates for tailored communities for glycerol electro-oxidation. From an acetate concentration pulse experiment, growth rates and half saturation rate constants for the biofilm of K_S = 1.4 mol mˆ-3 and d(q_max,Ac X_bf)/dt = 933 mmol mˆ-2 dˆ-2 are obtained. Furthermore, 1,3-propanediol and glycerol concentration pulse experiments show that the reaction from glycerol to 1,3-propanediol is reversed at high 1,3-propanediol concentrations. The presented methodology allows one to study pathways and extract rate constants through simple experiments in a running system without irreversibly altering the microbial community or destroying the biofilm.

@article{krewer_reviewdynamic_2018,
	title = {Review—{Dynamic} {Models} of {Li}-{Ion} {Batteries} for {Diagnosis} and {Operation}: {A} {Review} and {Perspective}},
	volume = {165},
	copyright = {All rights reserved},
	issn = {0013-4651, 1945-7111},
	shorttitle = {Review—{Dynamic} {Models} of {Li}-{Ion} {Batteries} for {Diagnosis} and {Operation}},
	url = {http://jes.ecsdl.org/lookup/doi/10.1149/2.1061814jes},
	doi = {10.1149/2.1061814jes},
	language = {en},
	number = {16},
	urldate = {2018-12-03},
	journal = {Journal of The Electrochemical Society},
	author = {Krewer, Ulrike and Röder, Fridolin and Harinath, Eranda and Braatz, Richard D. and Bedürftig, Benjamin and Findeisen, Rolf},
	year = {2018},
	pages = {A3656--A3673},
}

@article{lin_multiphysics_2018,
	title = {Multiphysics {Modeling} for {Detailed} {Analysis} of {Multi}-{Layer} {Lithium}-{Ion} {Pouch} {Cells}},
	volume = {11},
	copyright = {All rights reserved},
	issn = {1996-1073},
	url = {http://www.mdpi.com/1996-1073/11/11/2998},
	doi = {10.3390/en11112998},
	abstract = {Multiphysics modeling permits a detailed investigation of complex physical interactions and heterogeneous performance in multiple electro-active layers of a large-format Li-ion cell. For this purpose, a novel 3D multiphysics model with high computational efficiency was developed to investigate detailed multiphysics heterogeneity in different layers of a large-format pouch cell at various discharge rates. This model has spatial distribution and temporal evolution of local electric current density, solid lithium concentration and temperature distributions in different electro-active layers, based on a real pouch cell geometry. Other than previous models, we resolve the discharge processes at various discharge C-rates, analyzing internal inhomogeneity based on multiple electro-active layers of a large-format pouch cell. The results reveal that the strong inhomogeneity in multiple layers at a high C-rate is caused by the large heat generation and poor heat dissipation in the direction through the cell thickness. The thermal inhomogeneity also strongly interacts with the local electrochemical and electric performance in the investigated cell.},
	language = {en},
	number = {11},
	urldate = {2018-11-02},
	journal = {Energies},
	author = {Lin, Nan and Röder, Fridolin and Krewer, Ulrike},
	month = nov,
	year = {2018},
	pages = {2998},
}

Multiphysics modeling permits a detailed investigation of complex physical interactions and heterogeneous performance in multiple electro-active layers of a large-format Li-ion cell. For this purpose, a novel 3D multiphysics model with high computational efficiency was developed to investigate detailed multiphysics heterogeneity in different layers of a large-format pouch cell at various discharge rates. This model has spatial distribution and temporal evolution of local electric current density, solid lithium concentration and temperature distributions in different electro-active layers, based on a real pouch cell geometry. Other than previous models, we resolve the discharge processes at various discharge C-rates, analyzing internal inhomogeneity based on multiple electro-active layers of a large-format pouch cell. The results reveal that the strong inhomogeneity in multiple layers at a high C-rate is caused by the large heat generation and poor heat dissipation in the direction through the cell thickness. The thermal inhomogeneity also strongly interacts with the local electrochemical and electric performance in the investigated cell.

@article{haisch_influence_2018,
	title = {The influence of adsorbed substances on alkaline methanol electro-oxidation},
	copyright = {All rights reserved},
	issn = {00134686},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S0013468618323120},
	doi = {10.1016/j.electacta.2018.10.073},
	language = {en},
	urldate = {2018-10-27},
	journal = {Electrochimica Acta},
	author = {Haisch, Theresa and Kubannek, Fabian and Baranton, Stéve and Coutanceau, Christophe and Krewer, Ulrike},
	month = oct,
	year = {2018},
}

@article{emenike_model-based_2018,
	title = {Model-based optimization of biopharmaceutical manufacturing in {Pichia} pastoris based on dynamic flux balance analysis},
	volume = {118},
	copyright = {All rights reserved},
	issn = {00981354},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S0098135418307403},
	doi = {10.1016/j.compchemeng.2018.07.013},
	language = {en},
	urldate = {2018-10-25},
	journal = {Computers \& Chemical Engineering},
	author = {Emenike, Victor N. and Schenkendorf, René and Krewer, Ulrike},
	month = oct,
	year = {2018},
	pages = {1--13},
}

@article{schon_electrochemical_2018,
	title = {Electrochemical analysis of the reaction mechanism of sulfur reduction as a function of state of charge},
	copyright = {All rights reserved},
	issn = {00134686},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S0013468618319388},
	doi = {10.1016/j.electacta.2018.08.153},
	language = {en},
	urldate = {2018-10-23},
	journal = {Electrochimica Acta},
	author = {Schön, Patrick and Hintz, Frederik and Krewer, Ulrike},
	month = oct,
	year = {2018},
}

@article{schulze_flatness-based_2018,
	title = {Flatness-{Based} {Design} of {Experiments} for {Model} {Selection}},
	volume = {51},
	copyright = {All rights reserved},
	issn = {24058963},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S2405896318318019},
	doi = {10.1016/j.ifacol.2018.09.140},
	language = {en},
	number = {15},
	urldate = {2018-10-09},
	journal = {IFAC-PapersOnLine},
	author = {Schulze, Moritz and Schenkendorf, René},
	year = {2018},
	pages = {233--238},
}

@article{cheema_operating_2018,
	title = {Operating envelope of {Haber}–{Bosch} process design for power-to-ammonia},
	volume = {8},
	copyright = {All rights reserved},
	issn = {2046-2069},
	url = {http://xlink.rsc.org/?DOI=C8RA06821F},
	doi = {10.1039/C8RA06821F},
	language = {en},
	number = {61},
	urldate = {2018-10-12},
	journal = {RSC Advances},
	author = {Cheema, Izzat Iqbal and Krewer, Ulrike},
	year = {2018},
	pages = {34926--34936},
}

@article{xie_toward_2018,
	title = {Toward a {Comprehensive} and {Efficient} {Robust} {Optimization} {Framework} for ({Bio})chemical {Processes}},
	volume = {6},
	copyright = {All rights reserved},
	issn = {2227-9717},
	url = {http://www.mdpi.com/2227-9717/6/10/183},
	doi = {10.3390/pr6100183},
	language = {en},
	number = {10},
	urldate = {2018-10-04},
	journal = {Processes},
	author = {Xie, Xiangzhong and Schenkendorf, René and Krewer, Ulrike},
	month = oct,
	year = {2018},
	pages = {183},
}

@article{attari_moghaddam_mikrokinetische_2018,
	title = {Mikrokinetische {Modellierung} der {Ammoniaksynthese} und {Katalysator}-{Deaktivierung} im dynamischen {Haber}-{Bosch}-{Verfahren}},
	volume = {90},
	copyright = {All rights reserved},
	issn = {0009286X},
	url = {http://doi.wiley.com/10.1002/cite.201855222},
	doi = {10.1002/cite.201855222},
	language = {en},
	number = {9},
	urldate = {2018-09-03},
	journal = {Chemie Ingenieur Technik},
	author = {Attari Moghaddam, A. and Krewer, U.},
	month = sep,
	year = {2018},
	pages = {1232--1232},
}

@article{kubannek_kinetics_2018,
	title = {Kinetics and rate limitations in a glycerol-fed microbial fuel cell},
	volume = {90},
	copyright = {All rights reserved},
	issn = {0009286X},
	url = {http://doi.wiley.com/10.1002/cite.201855070},
	doi = {10.1002/cite.201855070},
	language = {en},
	number = {9},
	urldate = {2018-09-03},
	journal = {Chemie Ingenieur Technik},
	author = {Kubannek, F. and Moß, C. and Schröder, U. and Krewer, U.},
	month = sep,
	year = {2018},
	pages = {1164--1165},
}

@article{xie_robustes_2018,
	title = {Robustes {Prozessdesign} in der {Pharmatechnik} mittels performanter {Ersatzfunktionen}},
	volume = {90},
	copyright = {All rights reserved},
	issn = {0009286X},
	url = {http://doi.wiley.com/10.1002/cite.201855249},
	doi = {10.1002/cite.201855249},
	number = {9},
	journal = {Chemie Ingenieur Technik},
	author = {Xie, X. and Schenkendorf, R. and Krewer, U.},
	month = sep,
	year = {2018},
	pages = {1243--1244},
}

@article{winnefeld_modelling_2018,
	title = {Modelling and designing cryogenic hydrogen tanks for future aircraft applications},
	volume = {11},
	copyright = {All rights reserved},
	issn = {19961073},
	doi = {10.3390/en11010105},
	abstract = {In the near future, the challenges to reduce the economic and social dependency on fossil fuels must be faced increasingly. A sustainable and efficient energy supply based on renewable energies enables large-scale applications of electro-fuels for, e.g., the transport sector. The high gravimetric energy density makes liquefied hydrogen a reasonable candidate for energy storage in a light-weight application, such as aviation. Current aircraft structures are designed to accommodate jet fuel and gas turbines allowing a limited retrofitting only. New designs, such as the blended-wing-body, enable a more flexible integration of new storage technologies and energy converters, e.g., cryogenic hydrogen tanks and fuel cells. Against this background, a tank-design model is formulated, which considers geometrical, mechanical and thermal aspects, as well as specific mission profiles while considering a power supply by a fuel cell. This design approach enables the determination of required tank mass and storage density, respectively. A new evaluation value is defined including the vented hydrogen mass throughout the flight enabling more transparent insights on mass shares. Subsequently, a systematic approach in tank partitioning leads to associated compromises regarding the tank weight. The analysis shows that cryogenic hydrogen tanks are highly competitive with kerosene tanks in terms of overall mass, which is further improved by the use of a fuel cell.},
	number = {1},
	journal = {Energies},
	author = {Winnefeld, Christopher and Kadyk, Thomas and Bensmann, Boris and Krewer, Ulrike and Hanke-Rauschenbach, Richard},
	year = {2018},
	keywords = {Aviation, Energy storage, Fuel tanks, Hydrogen storage, Proton-exchange membrane fuel cell},
}

In the near future, the challenges to reduce the economic and social dependency on fossil fuels must be faced increasingly. A sustainable and efficient energy supply based on renewable energies enables large-scale applications of electro-fuels for, e.g., the transport sector. The high gravimetric energy density makes liquefied hydrogen a reasonable candidate for energy storage in a light-weight application, such as aviation. Current aircraft structures are designed to accommodate jet fuel and gas turbines allowing a limited retrofitting only. New designs, such as the blended-wing-body, enable a more flexible integration of new storage technologies and energy converters, e.g., cryogenic hydrogen tanks and fuel cells. Against this background, a tank-design model is formulated, which considers geometrical, mechanical and thermal aspects, as well as specific mission profiles while considering a power supply by a fuel cell. This design approach enables the determination of required tank mass and storage density, respectively. A new evaluation value is defined including the vented hydrogen mass throughout the flight enabling more transparent insights on mass shares. Subsequently, a systematic approach in tank partitioning leads to associated compromises regarding the tank weight. The analysis shows that cryogenic hydrogen tanks are highly competitive with kerosene tanks in terms of overall mass, which is further improved by the use of a fuel cell.

@article{mueller_design_2018,
	title = {Design {Considerations} for the {Electrical} {Power} {Supply} of {Future} {Civil} {Aircraft} with {Active} {High}-{Lift} {Systems}},
	volume = {11},
	copyright = {All rights reserved},
	issn = {1996-1073},
	url = {http://www.mdpi.com/1996-1073/11/1/179},
	doi = {10.3390/en11010179},
	abstract = {This paper reviews the recent research progress in the incorporation of plasmonic nanostructures with photovoltaic devices and the potential for surface plasmon enhanced absorption. We first outline a variety of cell architectures incorporating metal nanostructures. We then review the experimental fabrication methods and measurements to date, as well as systematic theoretical studies of the optimal nanostructure shapes. Finally we discuss photovoltaic absorber materials that could benefit from surface plasmon enhanced absorption.},
	number = {2},
	journal = {Energies},
	author = {Mueller, J.-K. and Bensmann, A. and Bensmann, B. and Fischer, T. and Kadyk, T. and Narjes, G. and Kauth, F. and Ponick, B. and Seume, J. and Krewer, U. and Hanke-Rauschenbach, R. and Mertens, A.},
	month = jan,
	year = {2018},
	pmid = {20814916},
	keywords = {photovoltaic devices, solar cells, surface plasmon resonance, thin films},
	pages = {179},
}

This paper reviews the recent research progress in the incorporation of plasmonic nanostructures with photovoltaic devices and the potential for surface plasmon enhanced absorption. We first outline a variety of cell architectures incorporating metal nanostructures. We then review the experimental fabrication methods and measurements to date, as well as systematic theoretical studies of the optimal nanostructure shapes. Finally we discuss photovoltaic absorber materials that could benefit from surface plasmon enhanced absorption.

@article{xie_moment-independent_2018,
	title = {Moment-{Independent} {Sensitivity} {Analysis} of {Enzyme}-{Catalyzed} {Reactions} with {Correlated} {Model} {Parameters}},
	volume = {51},
	copyright = {All rights reserved},
	issn = {24058963},
	doi = {10.1016/j.ifacol.2018.04.004},
	abstract = {The dynamic models used for biological and chemical process analysis and design usually include a significant number of uncertain model parameters. Sensitivity analysis is frequently applied to provide quantitative information regarding the influence of the parameters, as well as their uncertainties, on the model output. Various techniques are available in the literature to calculate parameter sensitivities based on local derivatives or changes in dedicated statistical moments of the model output. However, these methods may lead to an inevitable loss of information for a proper sensitivity analysis and are not directly available for problems with correlated model parameters. In this work, we demonstrate the use of a moment-independent sensitivity analysis concept in the presence and absence of parameter correlations and investigate the correlation effect in more detail. Moment-independent sensitivity analysis calculates parameter sensitivities based on changes in the entire probability density distribution of the model output and is formulated independently of whether the parameters are correlated or not. Technically, a single-loop Monte Carlo simulation method in combination with polynomial chaos expansion is implemented to reduce the computational cost significantly. A sampling procedure derived from Gaussian copula formalism is used to generate sample points for arbitrarily correlated uncertain parameters. The proposed concept is demonstrated with a case study of an enzyme-catalyzed reaction network. We observe evident differences in the parameter sensitivities for cases with independent and correlated model parameters.},
	number = {2},
	journal = {IFAC-PapersOnLine},
	author = {Xie, Xiangzhong and Ohs, Rüdiger and Spiess, Antje and Krewer, Ulrike and Schenkendorf, René},
	year = {2018},
	keywords = {Gaussian copula, enzyme-catalyzed reactions, moment-independent, parameter correlations, polynomial chaos expansion, sensitivity analysis},
	pages = {753--758},
}

The dynamic models used for biological and chemical process analysis and design usually include a significant number of uncertain model parameters. Sensitivity analysis is frequently applied to provide quantitative information regarding the influence of the parameters, as well as their uncertainties, on the model output. Various techniques are available in the literature to calculate parameter sensitivities based on local derivatives or changes in dedicated statistical moments of the model output. However, these methods may lead to an inevitable loss of information for a proper sensitivity analysis and are not directly available for problems with correlated model parameters. In this work, we demonstrate the use of a moment-independent sensitivity analysis concept in the presence and absence of parameter correlations and investigate the correlation effect in more detail. Moment-independent sensitivity analysis calculates parameter sensitivities based on changes in the entire probability density distribution of the model output and is formulated independently of whether the parameters are correlated or not. Technically, a single-loop Monte Carlo simulation method in combination with polynomial chaos expansion is implemented to reduce the computational cost significantly. A sampling procedure derived from Gaussian copula formalism is used to generate sample points for arbitrarily correlated uncertain parameters. The proposed concept is demonstrated with a case study of an enzyme-catalyzed reaction network. We observe evident differences in the parameter sensitivities for cases with independent and correlated model parameters.

@article{emenike_systematic_2018,
	title = {A systematic reactor design approach for the synthesis of active pharmaceutical ingredients},
	volume = {126},
	copyright = {All rights reserved},
	issn = {18733441},
	doi = {10.1016/j.ejpb.2017.05.007},
	abstract = {Today's highly competitive pharmaceutical industry is in dire need of an accelerated transition from the drug development phase to the drug production phase. At the heart of this transition are chemical reactors that facilitate the synthesis of active pharmaceutical ingredients (APIs) and whose design can affect subsequent processing steps. Inspired by this challenge, we present a model-based approach for systematic reactor design. The proposed concept is based on the elementary process functions (EPF) methodology to select an optimal reactor configuration from existing state-of-the-art reactor types or can possibly lead to the design of novel reactors. As a conceptual study, this work summarizes the essential steps in adapting the EPF approach to optimal reactor design problems in the field of API syntheses. Practically, the nucleophilic aromatic substitution of 2,4-difluoronitrobenzene was analyzed as a case study of pharmaceutical relevance. Here, a small-scale tubular coil reactor with controlled heating was identified as the optimal set-up reducing the residence time by 33\% in comparison to literature values.},
	journal = {European Journal of Pharmaceutics and Biopharmaceutics},
	author = {Emenike, Victor N. and Schenkendorf, René and Krewer, Ulrike},
	year = {2018},
	keywords = {Active pharmaceutical ingredients, Continuous pharmaceutical manufacturing, Elementary process functions, Intensified reactors, Nucleophilic aromatic substitution, Optimization},
	pages = {75--88},
}

Today's highly competitive pharmaceutical industry is in dire need of an accelerated transition from the drug development phase to the drug production phase. At the heart of this transition are chemical reactors that facilitate the synthesis of active pharmaceutical ingredients (APIs) and whose design can affect subsequent processing steps. Inspired by this challenge, we present a model-based approach for systematic reactor design. The proposed concept is based on the elementary process functions (EPF) methodology to select an optimal reactor configuration from existing state-of-the-art reactor types or can possibly lead to the design of novel reactors. As a conceptual study, this work summarizes the essential steps in adapting the EPF approach to optimal reactor design problems in the field of API syntheses. Practically, the nucleophilic aromatic substitution of 2,4-difluoronitrobenzene was analyzed as a case study of pharmaceutical relevance. Here, a small-scale tubular coil reactor with controlled heating was identified as the optimal set-up reducing the residence time by 33% in comparison to literature values.

@article{kubannek_revealing_2018,
	title = {Revealing metabolic storage processes in electrode respiring bacteria by differential electrochemical mass spectrometry},
	volume = {121},
	copyright = {All rights reserved},
	issn = {1878562X},
	doi = {10.1016/j.bioelechem.2018.01.014},
	abstract = {In this work we employ differential electrochemical mass spectrometry (DEMS) in combination with static and dynamic electrochemical techniques for the study of metabolic processes of electrochemically active bacteria. CO2production during acetate oxidation by electrode respiring bacteria was measured, in-vivo and online with a sensitivity of 6.5 ⋅ 10−13mol/s. The correlation of ion current and electrical current provides insight into the interaction of metabolic processes and extra-cellular electron transfer. In low-turnover CVs, two competing potential dependent electron transfer mechanisms were observed and formal potentials of two redox systems that are involved in complete oxidation of acetate to CO2were determined. By balancing charge and carbon flows during dynamic measurements, two significant storage mechanisms in electrochemically active bacteria were identified: 1) a charge storage mechanism that allows substrate oxidation to proceed at a constant rate despite of external current flowing in cathodic direction. 2) a carbon storage mechanism that allows the biofilm to take up acetate at an unchanged rate at very low potentials even though the oxidation to CO2stops. These storage capabilities allow a limited decoupling of electrical current and CO2production rate.},
	journal = {Bioelectrochemistry},
	author = {Kubannek, F. and Schröder, U. and Krewer, U.},
	year = {2018},
	keywords = {Charge and carbon storage, Differential electrochemical mass spectrometry, Mass spectrometric cyclic voltammetry, Microbial fuel cell, Online measurement of CO2production},
	pages = {160--168},
}

In this work we employ differential electrochemical mass spectrometry (DEMS) in combination with static and dynamic electrochemical techniques for the study of metabolic processes of electrochemically active bacteria. CO2production during acetate oxidation by electrode respiring bacteria was measured, in-vivo and online with a sensitivity of 6.5 ⋅ 10−13mol/s. The correlation of ion current and electrical current provides insight into the interaction of metabolic processes and extra-cellular electron transfer. In low-turnover CVs, two competing potential dependent electron transfer mechanisms were observed and formal potentials of two redox systems that are involved in complete oxidation of acetate to CO2were determined. By balancing charge and carbon flows during dynamic measurements, two significant storage mechanisms in electrochemically active bacteria were identified: 1) a charge storage mechanism that allows substrate oxidation to proceed at a constant rate despite of external current flowing in cathodic direction. 2) a carbon storage mechanism that allows the biofilm to take up acetate at an unchanged rate at very low potentials even though the oxidation to CO2stops. These storage capabilities allow a limited decoupling of electrical current and CO2production rate.

@article{titscher_increasing_2018,
	title = {Increasing {Energy} {Densities} of {Sulfur} {Cathodes} using {Dispersing} and {Calendering} {Processes} for {Lithium}–{Sulfur} {Batteries}},
	volume = {6},
	copyright = {All rights reserved},
	issn = {21944296},
	doi = {10.1002/ente.201700916},
	abstract = {© 2018 Wiley-VCH Verlag GmbH \& Co. KGaA, Weinheim Lithium–sulfur batteries are nearly ready to be commercialized. However, each material composition has specific challenges regarding its adaption to state of the art production lines of lithium-ion batteries. The influence of the dispersing and calendering process on the battery performance is investigated with an easy-to-implement material approach and a solvent-based process. The slurry is treated by different dispersing intensities using an extruder and a triple roller mill, which leads to increased energy densities. The coating is calendered to increase the energy density by maintaining the specific capacity. The reactions within the sulfur cathodes are investigated by evaluating the potentials of the upper and lower voltage plateaus. It was determined that the variation of the process parameters leads to a changed reactivity of the polysulfide reactions but not to a shift of the sulfur utilization within the sulfur cathodes. The process parameters influence the pore structure of the cathode, resulting in different sensitivities for higher C-rates.},
	number = {6},
	journal = {Energy Technology},
	author = {Titscher, Paul and Schön, Patrick and Horst, Marcella and Krewer, Ulrike and Kwade, Arno},
	year = {2018},
	keywords = {batteries, calendering, electrochemistry, materials processing, mechanical properties},
	pages = {1139--1147},
}

© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Lithium–sulfur batteries are nearly ready to be commercialized. However, each material composition has specific challenges regarding its adaption to state of the art production lines of lithium-ion batteries. The influence of the dispersing and calendering process on the battery performance is investigated with an easy-to-implement material approach and a solvent-based process. The slurry is treated by different dispersing intensities using an extruder and a triple roller mill, which leads to increased energy densities. The coating is calendered to increase the energy density by maintaining the specific capacity. The reactions within the sulfur cathodes are investigated by evaluating the potentials of the upper and lower voltage plateaus. It was determined that the variation of the process parameters leads to a changed reactivity of the polysulfide reactions but not to a shift of the sulfur utilization within the sulfur cathodes. The process parameters influence the pore structure of the cathode, resulting in different sensitivities for higher C-rates.

@article{harting_state--health_2018,
	title = {State-of-{Health} {Identification} of {Lithium}-{Ion} {Batteries} {Based} on {Nonlinear} {Frequency} {Response} {Analysis}: {First} {Steps} with {Machine} {Learning}},
	volume = {8},
	copyright = {All rights reserved},
	issn = {2076-3417},
	url = {http://www.mdpi.com/2076-3417/8/5/821},
	doi = {10.3390/app8050821},
	abstract = {In this study, we show an effective data-driven identification of the State-of-Health of Lithium-ion batteries by Nonlinear Frequency Response Analysis. A degradation model based on support vector regression is derived from highly informative Nonlinear Frequency Response Analysis data sets. First, an ageing test of a Lithium-ion battery at 25 \°C is presented and the impact of relevant ageing mechanisms on the nonlinear dynamics of the cells is analysed. A correlation measure is used to identify the most sensitive frequency range for ageing tests. Here, the mid-frequency range from 1 Hz to 100 Hz shows the strongest correlation to Lithium-ion battery degradation. The focus on the mid-frequency range leads to a dramatic reduction in measurement time of up to 92\% compared to standard measurement protocols. Next, informative features are extracted and used to parametrise the support vector regression model for the State of Health degradation. The performance of the degradation model is validated with additional cells and validation data sets, respectively. We show that the degradation model accurately predicts the State of Health values. Validation data demonstrate the usefulness of the Nonlinear Frequency Response Analysis as an effective and fast State of Health identification method and as a versatile tool in the diagnosis of ageing of Lithium-ion batteries in general.},
	number = {5},
	journal = {Applied Sciences},
	author = {Harting, Nina and Schenkendorf, René and Wolff, Nicolas and Krewer, Ulrike},
	year = {2018},
	pages = {821},
}

In this study, we show an effective data-driven identification of the State-of-Health of Lithium-ion batteries by Nonlinear Frequency Response Analysis. A degradation model based on support vector regression is derived from highly informative Nonlinear Frequency Response Analysis data sets. First, an ageing test of a Lithium-ion battery at 25 °C is presented and the impact of relevant ageing mechanisms on the nonlinear dynamics of the cells is analysed. A correlation measure is used to identify the most sensitive frequency range for ageing tests. Here, the mid-frequency range from 1 Hz to 100 Hz shows the strongest correlation to Lithium-ion battery degradation. The focus on the mid-frequency range leads to a dramatic reduction in measurement time of up to 92% compared to standard measurement protocols. Next, informative features are extracted and used to parametrise the support vector regression model for the State of Health degradation. The performance of the degradation model is validated with additional cells and validation data sets, respectively. We show that the degradation model accurately predicts the State of Health values. Validation data demonstrate the usefulness of the Nonlinear Frequency Response Analysis as an effective and fast State of Health identification method and as a versatile tool in the diagnosis of ageing of Lithium-ion batteries in general.

@article{kadyk_analysis_2018,
	title = {Analysis and {Design} of {Fuel} {Cell} {Systems} for {Aviation}},
	volume = {11},
	copyright = {All rights reserved},
	issn = {1996-1073},
	url = {http://www.mdpi.com/1996-1073/11/2/375},
	doi = {10.3390/en11020375},
	abstract = {In this paper, the design of fuel cells for the main energy supply of passenger transportation aircraft is discussed. Using a physical model of a fuel cell, general design considerations are derived. Considering different possible design objectives, the trade-off between power density and efficiency is discussed. A universal cost–benefit curve is derived to aid the design process. A weight factor wP is introduced, which allows incorporating technical (e.g., system mass and efficiency) as well as non-technical design objectives (e.g., operating cost, emission goals, social acceptance or technology affinity, political factors). The optimal fuel cell design is not determined by the characteristics of the fuel cell alone, but also by the characteristics of the other system components. The fuel cell needs to be designed in the context of the whole energy system. This is demonstrated by combining the fuel cell model with simple and detailed design models of a liquid hydrogen tank. The presented methodology and models allows assessing the potential of fuel cell systems for mass reduction of future passenger aircraft.},
	number = {2},
	journal = {Energies},
	author = {Kadyk, Thomas and Winnefeld, Christopher and Hanke-Rauschenbach, Richard and Krewer, Ulrike},
	year = {2018},
	pages = {375},
}

In this paper, the design of fuel cells for the main energy supply of passenger transportation aircraft is discussed. Using a physical model of a fuel cell, general design considerations are derived. Considering different possible design objectives, the trade-off between power density and efficiency is discussed. A universal cost–benefit curve is derived to aid the design process. A weight factor wP is introduced, which allows incorporating technical (e.g., system mass and efficiency) as well as non-technical design objectives (e.g., operating cost, emission goals, social acceptance or technology affinity, political factors). The optimal fuel cell design is not determined by the characteristics of the fuel cell alone, but also by the characteristics of the other system components. The fuel cell needs to be designed in the context of the whole energy system. This is demonstrated by combining the fuel cell model with simple and detailed design models of a liquid hydrogen tank. The presented methodology and models allows assessing the potential of fuel cell systems for mass reduction of future passenger aircraft.

@article{xie_robust_2018,
	title = {Robust {Optimization} of {Dynamical} {Systems} with {Correlated} {Random} {Variables} using the {Point} {Estimate} {Method}},
	volume = {51},
	copyright = {All rights reserved},
	issn = {24058963},
	doi = {10.1016/j.ifacol.2018.03.073},
	abstract = {Robust optimization of dynamical systems requires the proper uncertainty quantification. Monte Carlo simulations and polynomial chaos expansion are frequently used methods for uncertainty quantification and have been applied to a number of problems in process design and optimization. Both methods, however, are either computationally prohibitive for robust optimization or inappropriate for correlated random variables. The aim of this study is to introduce the point estimate method for optimization of dynamical systems with correlated random variables. The point estimate method requires only a few deterministic evaluations of the analyzed process model and estimates the statistical moments for robust optimization. The derived sample points can be adapted to random variables of arbitrary distributions and correlations. The contribution of this paper consists of presenting the point estimate method for correlated random variables in the field of model-based robust process design. The performance of the method is demonstrated with a case study of a continuous tubular reactor.},
	number = {2},
	journal = {IFAC-PapersOnLine},
	author = {Xie, Xiangzhong and Krewer, Ulrike and Schenkendorf, René},
	year = {2018},
	keywords = {correlated model parameters, point estimate method, robust optimization, uncertainty quantification},
	pages = {427--432},
}

Robust optimization of dynamical systems requires the proper uncertainty quantification. Monte Carlo simulations and polynomial chaos expansion are frequently used methods for uncertainty quantification and have been applied to a number of problems in process design and optimization. Both methods, however, are either computationally prohibitive for robust optimization or inappropriate for correlated random variables. The aim of this study is to introduce the point estimate method for optimization of dynamical systems with correlated random variables. The point estimate method requires only a few deterministic evaluations of the analyzed process model and estimates the statistical moments for robust optimization. The derived sample points can be adapted to random variables of arbitrary distributions and correlations. The contribution of this paper consists of presenting the point estimate method for correlated random variables in the field of model-based robust process design. The performance of the method is demonstrated with a case study of a continuous tubular reactor.

@article{lin_efficient_2018,
	title = {Efficient {Global} {Sensitivity} {Analysis} of {3D} {Multiphysics} {Model} for {Li}-{Ion} {Batteries}},
	volume = {165},
	copyright = {All rights reserved},
	issn = {0013-4651},
	url = {http://jes.ecsdl.org/lookup/doi/10.1149/2.1301805jes},
	doi = {10.1149/2.1301805jes},
	abstract = {Parameter sensitivity analysis of mechanistic battery models has the power to quantify the individual and joint effects of parameters on the performance of lithium-ion cells. This information can be beneficial for industrial cell designs, cell testing, and battery management system (BMS) configurations. The numerical quantification of these parameter sensitivities, however, is challenging in terms of computational costs and is an active field of research. In this paper, based on a 3D multiphysics model, we conduct a global sensitivity analysis for the utilizable cell discharge capacity and the maximum cell temperature at the discharge rate of 1C. The least angle regression version of the polynomial chaos expansion (PCE) concept has been identified as an optimal trade-off between approximation power and computational complexity. As a result, the sensitivities of all parameters in the 3D multiphysics model were studied using a hierarchical design and a stepwise design. We conclude that the cell discharge capacity and the thermal behavior at 1C discharge are most sensitive to the electrode parameters and their pore structure. The results reveal different dependencies and lead to new insights for cell design and operation.},
	number = {7},
	journal = {Journal of The Electrochemical Society},
	author = {Lin, Nan and Xie, Xiangzhong and Schenkendorf, René and Krewer, Ulrike},
	year = {2018},
	pages = {A1169--A1183},
}

Parameter sensitivity analysis of mechanistic battery models has the power to quantify the individual and joint effects of parameters on the performance of lithium-ion cells. This information can be beneficial for industrial cell designs, cell testing, and battery management system (BMS) configurations. The numerical quantification of these parameter sensitivities, however, is challenging in terms of computational costs and is an active field of research. In this paper, based on a 3D multiphysics model, we conduct a global sensitivity analysis for the utilizable cell discharge capacity and the maximum cell temperature at the discharge rate of 1C. The least angle regression version of the polynomial chaos expansion (PCE) concept has been identified as an optimal trade-off between approximation power and computational complexity. As a result, the sensitivities of all parameters in the 3D multiphysics model were studied using a hierarchical design and a stepwise design. We conclude that the cell discharge capacity and the thermal behavior at 1C discharge are most sensitive to the electrode parameters and their pore structure. The results reveal different dependencies and lead to new insights for cell design and operation.

@article{krewer_impact_2018,
	title = {Impact of carbonation processes in anion exchange membrane fuel cells},
	volume = {263},
	copyright = {All rights reserved},
	issn = {00134686},
	doi = {10.1016/j.electacta.2017.12.093},
	abstract = {Alkaline anion exchange membrane fuel cell (AEMFC) is a promising technology to replace precious metals used today as fuel cell catalysts. However, AEMFC does not yet demonstrate high performance when running on ambient air where they are exposed to CO2. The resulting carbonation reaction reduces membrane conductivity. This paper analyses and quantifies the effect of CO2from ambient air on the concentration profiles in the membrane and the anode and, thus, assesses the CO2impact on fuel cell performance. The physico-chemical model contains chemical and electrochemical reactions, liquid-gas phase equilibria as well as the transport processes in the cell. Results imply that a significant part of fed CO2is absorbed in the cathode and is transported as carbonate ions to the anode. Concentration profiles in the membrane reveal an enrichment zone of CO2in the membrane close to the anode, negligible HCO3−and a wide distribution of CO32−across the membrane. The carbonate distribution affects overall anion exchange membrane conductivity. For practical relevant current densities of i{\textbackslash}textbackslashtextbackslashtextgreater500mAcm−2and typical excess ratios of 1.5 for the hydrogen feed, less than 10\% of the anions in the membrane are CO32−. We show that while increasing cell temperature has an ambiguous effect on the carbonation process and on the total effect of CO2on the cell, current density has a significant effect. The impact of CO2on AEMFC performance can be significantly decreased when operating the cell at high current densities above 1000mAcm−2.},
	journal = {Electrochimica Acta},
	author = {Krewer, Ulrike and Weinzierl, Christine and Ziv, Noga and Dekel, Dario R.},
	year = {2018},
	keywords = {Alkaline fuel cell, Anion exchange membrane fuel cell, Carbon dioxide, Carbonation, Mathematical modelling},
	pages = {433--446},
}

Alkaline anion exchange membrane fuel cell (AEMFC) is a promising technology to replace precious metals used today as fuel cell catalysts. However, AEMFC does not yet demonstrate high performance when running on ambient air where they are exposed to CO2. The resulting carbonation reaction reduces membrane conductivity. This paper analyses and quantifies the effect of CO2from ambient air on the concentration profiles in the membrane and the anode and, thus, assesses the CO2impact on fuel cell performance. The physico-chemical model contains chemical and electrochemical reactions, liquid-gas phase equilibria as well as the transport processes in the cell. Results imply that a significant part of fed CO2is absorbed in the cathode and is transported as carbonate ions to the anode. Concentration profiles in the membrane reveal an enrichment zone of CO2in the membrane close to the anode, negligible HCO3−and a wide distribution of CO32−across the membrane. The carbonate distribution affects overall anion exchange membrane conductivity. For practical relevant current densities of i\textbackslashtextbackslashtextgreater500mAcm−2and typical excess ratios of 1.5 for the hydrogen feed, less than 10% of the anions in the membrane are CO32−. We show that while increasing cell temperature has an ambiguous effect on the carbonation process and on the total effect of CO2on the cell, current density has a significant effect. The impact of CO2on AEMFC performance can be significantly decreased when operating the cell at high current densities above 1000mAcm−2.

@article{wolff_nonlinear_2018-1,
	title = {Nonlinear {Frequency} {Response} {Analysis} on {Lithium}-{Ion} {Batteries}: {A} {Model}-{Based} {Assessment}},
	volume = {260},
	copyright = {All rights reserved},
	issn = {00134686},
	doi = {10.1016/j.electacta.2017.12.097},
	abstract = {The nonlinear behavior of electrochemical systems, such as batteries bears essential information on their state and processes interacting within them. A Pseudo-two-Dimensional Lithium-ion battery model is used for Nonlinear Frequency Response Analysis (NFRA). Focus is laid on identification of processes in Lithium-ion batteries. The most commonly applied dynamic electrochemical analysis method, Electrochemical Impedance Spectroscopy (EIS), is limited to linear deflections of the system. This denotes loss of information about nonlinear system behavior. In contrast, NFRA extends this approach to study the nonlinear behavior of the Lithium-ion battery. We show dependency of nonlinear responses on the input amplitude and several model parameters, such as diffusion coefficient, reaction rate constant and double layer capacitance. Parameter variation demonstrates the capability of this method for process identification by investigating the individual higher harmonics and the respective sum. Characteristic peaks can be attributed to electrode reactions and diffusion and frequency regions influenced by the signal can be identified. This work gives a deeper understanding of the nonlinear response of a Lithium-ion battery and as such of how to apply this analysis method for Lithium-ion battery state estimation. It is shown that the method NFRA is essential for reliable process identification. Battery characterization highly benefits from the combination of EIS and NFRA.},
	journal = {Electrochimica Acta},
	author = {Wolff, Nicolas and Harting, Nina and Heinrich, Marco and Röder, Fridolin and Krewer, Ulrike},
	year = {2018},
	keywords = {Dynamic analysis, Electrochemical impedance spectroscopy, Modeling, NFRA},
	pages = {614--622},
}

The nonlinear behavior of electrochemical systems, such as batteries bears essential information on their state and processes interacting within them. A Pseudo-two-Dimensional Lithium-ion battery model is used for Nonlinear Frequency Response Analysis (NFRA). Focus is laid on identification of processes in Lithium-ion batteries. The most commonly applied dynamic electrochemical analysis method, Electrochemical Impedance Spectroscopy (EIS), is limited to linear deflections of the system. This denotes loss of information about nonlinear system behavior. In contrast, NFRA extends this approach to study the nonlinear behavior of the Lithium-ion battery. We show dependency of nonlinear responses on the input amplitude and several model parameters, such as diffusion coefficient, reaction rate constant and double layer capacitance. Parameter variation demonstrates the capability of this method for process identification by investigating the individual higher harmonics and the respective sum. Characteristic peaks can be attributed to electrode reactions and diffusion and frequency regions influenced by the signal can be identified. This work gives a deeper understanding of the nonlinear response of a Lithium-ion battery and as such of how to apply this analysis method for Lithium-ion battery state estimation. It is shown that the method NFRA is essential for reliable process identification. Battery characterization highly benefits from the combination of EIS and NFRA.

@article{lenze_impacts_2018,
	title = {Impacts of {Variations} in {Manufacturing} {Parameters} on {Performance} of {Lithium}-{Ion}-{Batteries}},
	volume = {165},
	copyright = {All rights reserved},
	issn = {0013-4651},
	url = {http://jes.ecsdl.org/lookup/doi/10.1149/2.1081802jes},
	doi = {10.1149/2.1081802jes},
	abstract = {Cell performance of lithium-ion-batteries (LIB) can be tailored to particular hybrid or full electric vehicle applications by targeted adjustment of manufacturing parameters. Furthermore there is a large number of cathode material compositions which can be used. Knowing the correlations between these parameters, electrode structures and cell performance is important to reach the high requirements posed by electromobility.Within this study, impacts of essential manufacturing parameters, being active material mass loading, calendering stress load and carbon black content on the cell performance were investigated for two different, promising cathode materials. For NMC and LMO, the respectively highest calendering stress load and carbon black content yielded the best performance as losses due to poor electronic conductivity were reduced. The active material mass loading rather influenced the ratio between specific energy and specific power. Finally two optimally performing parameter configurations could be identified which were, depending on the required application: NMC with high mass loading and LMO with medium mass loading; in both cases the highest calendering load and carbon black content were applied. An analysis of statistical reproducibility dependent on various parameter configurations was carried out as well. A significant improvement of reproducibility could be achieved by increase of calendering stress load.},
	number = {2},
	journal = {Journal of The Electrochemical Society},
	author = {Lenze, Georg and Bockholt, Henrike and Schilcher, Christiane and Froböse, Linus and Jansen, Dietmar and Krewer, Ulrike and Kwade, Arno},
	year = {2018},
	pages = {A314--A322},
}

Cell performance of lithium-ion-batteries (LIB) can be tailored to particular hybrid or full electric vehicle applications by targeted adjustment of manufacturing parameters. Furthermore there is a large number of cathode material compositions which can be used. Knowing the correlations between these parameters, electrode structures and cell performance is important to reach the high requirements posed by electromobility.Within this study, impacts of essential manufacturing parameters, being active material mass loading, calendering stress load and carbon black content on the cell performance were investigated for two different, promising cathode materials. For NMC and LMO, the respectively highest calendering stress load and carbon black content yielded the best performance as losses due to poor electronic conductivity were reduced. The active material mass loading rather influenced the ratio between specific energy and specific power. Finally two optimally performing parameter configurations could be identified which were, depending on the required application: NMC with high mass loading and LMO with medium mass loading; in both cases the highest calendering load and carbon black content were applied. An analysis of statistical reproducibility dependent on various parameter configurations was carried out as well. A significant improvement of reproducibility could be achieved by increase of calendering stress load.

@incollection{schenkendorf_efficient_2017,
	title = {An {Efficient} {Polynomial} {Chaos} {Expansion} {Strategy} for {Active} {Fault} {Identification} of {Chemical} {Processes}},
	volume = {40},
	copyright = {All rights reserved},
	url = {https://linkinghub.elsevier.com/retrieve/pii/B9780444639653502816},
	abstract = {To gain profit from complex chemical processes, it is essential to ensure its proper operation, i.e. to avoid costly unexpected downtimes of underlying processing units. This paper explores a highly efficient active fault detection and isolation (FDI) framework, which facilitates the discriminability of a set of analysed model candidates including the reference model (nominal behaviour) as well as pre-defined failure models (faulty behaviour). Practically, an auxiliary, model-discriminating input is derived by solving a dynamic optimization problem. While using a model-based approach, the active FDI implementation has to be robustified against the inherent model parameter uncertainties. To this end, a non-intrusive polynomial chaos expansion (PCE) is used to address these uncertainties. To guarantee a computationally feasible performance, the original PCE setting has been considerably improved. Here, the basic idea is to render the design variables (auxiliary inputs) into random variables as well. Thus, the derived PCE results are not only sensitive to the model parameters but also to the design variables. To lower the computational burden further, a least angle regression strategy is applied utilizing the sparsity property of the PCE approach. The overall effectiveness of this One-Short Sparse Polynomial Chaos Expansion (OS2-PCE) concept for FDI is illustrated conceptually by analysing a tubular plug flow reactor.},
	booktitle = {Computer {Aided} {Chemical} {Engineering}},
	author = {Schenkendorf, René and Xie, Xiangzhong and Krewer, Ulrike},
	year = {2017},
	doi = {10.1016/B978-0-444-63965-3.50281-6},
	keywords = {Active Fault Detection and Isolation, Dynamic Optimization, Least Angle Regression, Polynomial Chaos Expansion},
	pages = {1675--1680},
}

To gain profit from complex chemical processes, it is essential to ensure its proper operation, i.e. to avoid costly unexpected downtimes of underlying processing units. This paper explores a highly efficient active fault detection and isolation (FDI) framework, which facilitates the discriminability of a set of analysed model candidates including the reference model (nominal behaviour) as well as pre-defined failure models (faulty behaviour). Practically, an auxiliary, model-discriminating input is derived by solving a dynamic optimization problem. While using a model-based approach, the active FDI implementation has to be robustified against the inherent model parameter uncertainties. To this end, a non-intrusive polynomial chaos expansion (PCE) is used to address these uncertainties. To guarantee a computationally feasible performance, the original PCE setting has been considerably improved. Here, the basic idea is to render the design variables (auxiliary inputs) into random variables as well. Thus, the derived PCE results are not only sensitive to the model parameters but also to the design variables. To lower the computational burden further, a least angle regression strategy is applied utilizing the sparsity property of the PCE approach. The overall effectiveness of this One-Short Sparse Polynomial Chaos Expansion (OS2-PCE) concept for FDI is illustrated conceptually by analysing a tubular plug flow reactor.

@article{harting_nonlinear_2017,
	title = {Nonlinear {Frequency} {Response} {Analysis} ({NFRA}) of {Lithium}-{Ion} {Batteries}},
	volume = {248},
	copyright = {All rights reserved},
	issn = {00134686},
	doi = {10.1016/j.electacta.2017.04.037},
	abstract = {Electrochemical Impedance Spectroscopy (EIS) is the most commonly used technique for dynamic analysis of Lithium-ion batteries. EIS, however, limits analysis to linear contributions of the processes. For Lithium-ion batteries with their nonlinear electrochemistry and physics, dynamics are only analysed with regard to linear system behaviour and therefore some dynamic information is not used. Nonlinear Frequency Response Analysis (NFRA) extends dynamic analysis to consider also nonlinearities. Higher excitation amplitudes are applied and higher order frequency responses Ynare measured. The spectra show distinct higher harmonic responses with strong characteristic nonlinear behaviour. We investigate amplitude and temperature dependency of higher harmonic responses as well as the impact of ageing of Lithium-ion batteries with NFRA. By correlating NFRA and EIS, solid diffusion, reaction and ionic transport contributions at and in the SEI can be separated and identified. Thereby the method of NFRA is seen as an important additional dynamic analysis method for Lithium-ion batteries.},
	journal = {Electrochimica Acta},
	author = {Harting, Nina and Wolff, Nicolas and Röder, Fridolin and Krewer, Ulrike},
	year = {2017},
	keywords = {Harmonic Analysis, Impedance Spectroscopy, Lithium-ion Battery, Nonlinear Frequency Response Analysis},
	pages = {133--139},
}

Electrochemical Impedance Spectroscopy (EIS) is the most commonly used technique for dynamic analysis of Lithium-ion batteries. EIS, however, limits analysis to linear contributions of the processes. For Lithium-ion batteries with their nonlinear electrochemistry and physics, dynamics are only analysed with regard to linear system behaviour and therefore some dynamic information is not used. Nonlinear Frequency Response Analysis (NFRA) extends dynamic analysis to consider also nonlinearities. Higher excitation amplitudes are applied and higher order frequency responses Ynare measured. The spectra show distinct higher harmonic responses with strong characteristic nonlinear behaviour. We investigate amplitude and temperature dependency of higher harmonic responses as well as the impact of ageing of Lithium-ion batteries with NFRA. By correlating NFRA and EIS, solid diffusion, reaction and ionic transport contributions at and in the SEI can be separated and identified. Thereby the method of NFRA is seen as an important additional dynamic analysis method for Lithium-ion batteries.

@article{na_highly_2017,
	title = {Highly integrated direct methanol fuel cell systems minimizing fuel loss with dynamic concentration control for portable applications},
	volume = {57},
	copyright = {All rights reserved},
	issn = {09591524},
	doi = {10.1016/j.jprocont.2017.06.014},
	abstract = {Direct methanol fuel cell (DMFC) systems are mostly composed of massive water recycling devices such as coolers, condensers or mixers even for small and light portable applications. Integrated systems, where system components serve more than one function, can be equipped with fewer components and have a lighter weight than conventional ones. However, the process integration can also bring about significant methanol evaporation in separators, resulting in low fuel efficiency. The here presented highly integrated system can minimize methanol loss with optimized concentration control to improve efficiency. Two system variants are compared with regard to concentration, temperature, water recovery controllability and efficiency. The simulation results are compared with the previously published mingled-outlet system and validated with experiments.},
	journal = {Journal of Process Control},
	author = {Na, Youngseung and Zenith, Federico and Krewer, Ulrike},
	year = {2017},
	keywords = {Concentration control, DMFC, Fuel cell systems, Process integration},
	pages = {140--147},
}

Direct methanol fuel cell (DMFC) systems are mostly composed of massive water recycling devices such as coolers, condensers or mixers even for small and light portable applications. Integrated systems, where system components serve more than one function, can be equipped with fewer components and have a lighter weight than conventional ones. However, the process integration can also bring about significant methanol evaporation in separators, resulting in low fuel efficiency. The here presented highly integrated system can minimize methanol loss with optimized concentration control to improve efficiency. Two system variants are compared with regard to concentration, temperature, water recovery controllability and efficiency. The simulation results are compared with the previously published mingled-outlet system and validated with experiments.

@article{jenssen_improved_2017,
	title = {Improved {PEM} fuel cell system operation with cascaded stack and ejector-based recirculation},
	volume = {195},
	copyright = {All rights reserved},
	issn = {03062619},
	doi = {10.1016/j.apenergy.2017.03.002},
	abstract = {An automotive fuel cell system combining a variable-geometry ejector and a fuel cell stack with cascaded anode is presented. It allows to decrease the minimum operational power range by increasing recirculation performance of the ejector. Design boundaries for the fuel cell anode are used to investigate four different designs of fuel cell stack with cascaded anode. For these designs, ejectors with variable-geometry are developed and their performance in combination with the fuel cell stacks are investigated using CFD simulations. A combination of a variable-geometry ejector with a two stage cascaded stack design is shown to exhibit a better recirculation performance at low power outputs than systems with conventional stack design. It is demonstrated experimentally that the new fuel cell design achieves similar performance and stability on a test bench compared to conventional stack design.},
	journal = {Applied Energy},
	author = {Jenssen, Dirk and Berger, Oliver and Krewer, Ulrike},
	year = {2017},
	keywords = {Design boundaries, Hydrogen supply system design, Stack design with cascaded anode, Variable-geometry ejector design process},
	pages = {324--333},
}

An automotive fuel cell system combining a variable-geometry ejector and a fuel cell stack with cascaded anode is presented. It allows to decrease the minimum operational power range by increasing recirculation performance of the ejector. Design boundaries for the fuel cell anode are used to investigate four different designs of fuel cell stack with cascaded anode. For these designs, ejectors with variable-geometry are developed and their performance in combination with the fuel cell stacks are investigated using CFD simulations. A combination of a variable-geometry ejector with a two stage cascaded stack design is shown to exhibit a better recirculation performance at low power outputs than systems with conventional stack design. It is demonstrated experimentally that the new fuel cell design achieves similar performance and stability on a test bench compared to conventional stack design.

@article{kalz_future_2017,
	title = {Future {Challenges} in {Heterogeneous} {Catalysis}: {Understanding} {Catalysts} under {Dynamic} {Reaction} {Conditions}},
	volume = {9},
	copyright = {All rights reserved},
	issn = {18673899},
	doi = {10.1002/cctc.201600996},
	abstract = {In the future, (electro-)chemical catalysts will have to be more tolerant towards a varying supply of energy and raw materials. This is mainly due to the fluctuating nature of renewable energies. For example, power-to-chemical processes require a shift from steady-state operation towards operation under dynamic reaction conditions. This brings along a number of demands for the design of both catalysts and reactors, because it is well-known that the structure of catalysts is very dynamic. However, in-depth studies of catalysts and catalytic reactors under such transient conditions have only started recently. This requires studies and advances in the fields of (i) operando spectroscopy including time-resolved methods, (ii) theory with predictive quality, (iii) kinetic modelling, (iv) design of catalysts by appropriate preparation concepts, and (v) novel/modular reactor designs. An intensive exchange between these scientific disciplines will enable a substantial gain of fundamental knowledge which is urgently required. This concept article highlights recent developments, challenges, and future directions for understanding catalysts under dynamic reaction conditions.},
	number = {1},
	journal = {ChemCatChem},
	author = {Kalz, Kai F. and Kraehnert, Ralph and Dvoyashkin, Muslim and Dittmeyer, Roland and Gläser, Roger and Krewer, Ulrike and Reuter, Karsten and Grunwaldt, Jan Dierk},
	year = {2017},
	pmid = {28239429},
	keywords = {electrocatalysis, energy storage, heterogeneous catalysis, molecular modelling, operando spectroscopy},
	pages = {17--29},
}

In the future, (electro-)chemical catalysts will have to be more tolerant towards a varying supply of energy and raw materials. This is mainly due to the fluctuating nature of renewable energies. For example, power-to-chemical processes require a shift from steady-state operation towards operation under dynamic reaction conditions. This brings along a number of demands for the design of both catalysts and reactors, because it is well-known that the structure of catalysts is very dynamic. However, in-depth studies of catalysts and catalytic reactors under such transient conditions have only started recently. This requires studies and advances in the fields of (i) operando spectroscopy including time-resolved methods, (ii) theory with predictive quality, (iii) kinetic modelling, (iv) design of catalysts by appropriate preparation concepts, and (v) novel/modular reactor designs. An intensive exchange between these scientific disciplines will enable a substantial gain of fundamental knowledge which is urgently required. This concept article highlights recent developments, challenges, and future directions for understanding catalysts under dynamic reaction conditions.

@incollection{xie_robust_2017,
	title = {Robust {Design} of {Chemical} {Processes} {Based} on a {One}-{Shot} {Sparce} {Polynomial} {Chaos} {Expansion} {Concept}},
	volume = {40},
	copyright = {All rights reserved},
	abstract = {The application of robust model-based design concepts for complex chemical processes is limited due to the repeated cpu-intensive uncertainty quantification step for any new tested process design configuration. Therefore, an efficient One-Shot Sparse Polynomial Chaos Expansion (OS2-PCE) based process design framework is introduced in this work. The key idea is to define the process design variables as uncertain quantities as well and, in consequence, they become an integral part of the robust optimization routine. Moreover, by utilizing the sparsity feature of the PCE approach, the implementation of a least angle regression (LAR) concept leads to a significant reduction in computational costs. The overall performance of the novel OS2-PCE approach is illustrated by a robust process design study of a jacketed tubular reactor. In comparison to state-of-the-art concepts, the proposed framework shows promising results in terms of efficiency and robustness.},
	booktitle = {Computer {Aided} {Chemical} {Engineering}},
	author = {Xie, Xiangzhong and Schenkendorf, René and Krewer, Ulrike},
	year = {2017},
	doi = {10.1016/B978-0-444-63965-3.50104-5},
	keywords = {chemical processes, least angle regression, optimization, polynomial chaos expansion, robust design, uncertainty},
	pages = {613--618},
}

The application of robust model-based design concepts for complex chemical processes is limited due to the repeated cpu-intensive uncertainty quantification step for any new tested process design configuration. Therefore, an efficient One-Shot Sparse Polynomial Chaos Expansion (OS2-PCE) based process design framework is introduced in this work. The key idea is to define the process design variables as uncertain quantities as well and, in consequence, they become an integral part of the robust optimization routine. Moreover, by utilizing the sparsity feature of the PCE approach, the implementation of a least angle regression (LAR) concept leads to a significant reduction in computational costs. The overall performance of the novel OS2-PCE approach is illustrated by a robust process design study of a jacketed tubular reactor. In comparison to state-of-the-art concepts, the proposed framework shows promising results in terms of efficiency and robustness.

@article{lenze_simulation-supported_2017,
	title = {Simulation-{Supported} {Analysis} of {Calendering} {Impacts} on the {Performance} of {Lithium}-{Ion}-{Batteries}},
	volume = {164},
	copyright = {All rights reserved},
	issn = {0013-4651},
	url = {http://jes.ecsdl.org/lookup/doi/10.1149/2.1141706jes},
	doi = {10.1149/2.1141706jes},
	abstract = {A combination of experimental and model based analysis was performed to investigate calendering impacts on the performance of lithium-ion-batteries. When discharging, not only geometric parameters, such as electrode thicknesses and porosities are affecting performance. Calendering also impacts on other parameters, such as the effective ionic conductivity within the electrolyte, the effective electronic conductivity of solid active material and the effective solid-liquid interfacial area. The simulation supported method is shown to complement experimental analysis to understand correlations between calendering and these parameters; it enables to identify cell internal parameters which are hard to measure and to analyze how the lithium transport is affected. In experiments, cells containing non-calendered cathodes performed significantly worse than ones with 22\%-calendered cathodes. Simulation indicated that this losses consist mainly of a deterioration of effective electronic conductivity leading to overpotentials close to the separator. Minor contributions to the losses in non-calendered cathodes caused by the geometric compaction and a reduction of effective solid-liquid interfacial area were found as well, whereas the impact of effective ionic conductivity turned out to be only insignificantly small. Calendering of electrodes is an important step within the manu-facturing process of lithium-ion-batteries as it affects energy density significantly. 1 An increase in energy density is crucial to achieve larger driving ranges for electric vehicles and thus to make them compet-itive on the market. Aim of this work is to establish an advanced model based method for the analysis of calendering impacts which gives additional insights into cell internal electrochemical correla-tions. Most studies about calendering impacts on battery electrodes are of experimental nature. 1–3 These investigations present mechanical and electrochemical characterization results of industrially produced and readily usable electrode samples. Usually mercury (Hg) porosime-try, scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), C-Rate, and cycling tests are performed. These methods are helpful to understand how calendering affects the ge-ometric and mechanical properties of particle-pore networks within electrodes. However, evaluation of correlations between structural changes and battery performance is rather phenomenological and empirical so that knowledge gained is limited. EIS measurements are commonly used for correlation between structural changes and performance determining physico-chemical processes and constants, such as electronic conductivity within the electrode; 4,5 to investigate calendering impacts on the aging behavior cycling experiments have been used 6 . However, it is still difficult to understand calendering im-pacts on performance entirely, as calendering affects several parame-ters simultaneously, making evaluations complex. Additional tools for analysis can improve this understanding and enable knowledge-driven optimization of manufacturing parameters. Physico-chemical battery models enable to simulate battery performance as a function of struc-tural parameters, such as electrode thickness and porosity, 7 as well as of parameters like solid-liquid interfacial area, electronic and ionic conductivities, which may be affected by calendering as well. 8 Fur-thermore, not only the resulting battery performance but underlying processes like lithium (Li) transport within electrolyte, electrodes and active material particles can be studied. 9 These features make simu-lation a promising complementary tool to experimental investigations for understanding calendering impacts in Li-ion-batteries and the re-lated structure-performance correlations. We see simulation therefore as essential to achieve an optimized battery production. Approaches of simulating structure-performance correlations in lithium-ion-batteries can be found in literature; they are rather theoretical, as they primarily},
	number = {6},
	journal = {Journal of The Electrochemical Society},
	author = {Lenze, Georg and Röder, Fridolin and Bockholt, Henrike and Haselrieder, Wolfgang and Kwade, Arno and Krewer, Ulrike},
	year = {2017},
	pages = {A1223--A1233},
}

A combination of experimental and model based analysis was performed to investigate calendering impacts on the performance of lithium-ion-batteries. When discharging, not only geometric parameters, such as electrode thicknesses and porosities are affecting performance. Calendering also impacts on other parameters, such as the effective ionic conductivity within the electrolyte, the effective electronic conductivity of solid active material and the effective solid-liquid interfacial area. The simulation supported method is shown to complement experimental analysis to understand correlations between calendering and these parameters; it enables to identify cell internal parameters which are hard to measure and to analyze how the lithium transport is affected. In experiments, cells containing non-calendered cathodes performed significantly worse than ones with 22%-calendered cathodes. Simulation indicated that this losses consist mainly of a deterioration of effective electronic conductivity leading to overpotentials close to the separator. Minor contributions to the losses in non-calendered cathodes caused by the geometric compaction and a reduction of effective solid-liquid interfacial area were found as well, whereas the impact of effective ionic conductivity turned out to be only insignificantly small. Calendering of electrodes is an important step within the manu-facturing process of lithium-ion-batteries as it affects energy density significantly. 1 An increase in energy density is crucial to achieve larger driving ranges for electric vehicles and thus to make them compet-itive on the market. Aim of this work is to establish an advanced model based method for the analysis of calendering impacts which gives additional insights into cell internal electrochemical correla-tions. Most studies about calendering impacts on battery electrodes are of experimental nature. 1–3 These investigations present mechanical and electrochemical characterization results of industrially produced and readily usable electrode samples. Usually mercury (Hg) porosime-try, scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), C-Rate, and cycling tests are performed. These methods are helpful to understand how calendering affects the ge-ometric and mechanical properties of particle-pore networks within electrodes. However, evaluation of correlations between structural changes and battery performance is rather phenomenological and empirical so that knowledge gained is limited. EIS measurements are commonly used for correlation between structural changes and performance determining physico-chemical processes and constants, such as electronic conductivity within the electrode; 4,5 to investigate calendering impacts on the aging behavior cycling experiments have been used 6 . However, it is still difficult to understand calendering im-pacts on performance entirely, as calendering affects several parame-ters simultaneously, making evaluations complex. Additional tools for analysis can improve this understanding and enable knowledge-driven optimization of manufacturing parameters. Physico-chemical battery models enable to simulate battery performance as a function of struc-tural parameters, such as electrode thickness and porosity, 7 as well as of parameters like solid-liquid interfacial area, electronic and ionic conductivities, which may be affected by calendering as well. 8 Fur-thermore, not only the resulting battery performance but underlying processes like lithium (Li) transport within electrolyte, electrodes and active material particles can be studied. 9 These features make simu-lation a promising complementary tool to experimental investigations for understanding calendering impacts in Li-ion-batteries and the re-lated structure-performance correlations. We see simulation therefore as essential to achieve an optimized battery production. Approaches of simulating structure-performance correlations in lithium-ion-batteries can be found in literature; they are rather theoretical, as they primarily

@incollection{emenike_model-based_2017,
	title = {Model-based optimization of the recombinant protein production in {Pichia} pastoris based on dynamic flux balance analysis and elementary process functions},
	volume = {40},
	copyright = {All rights reserved},
	isbn = {978-0-444-63965-3},
	abstract = {Pichia pastoris is an important host cell for the heterologous expression of recombinant proteins. In order to understand and design optimal biopharmaceutical processes with P. pastoris, unstructured and flux balance analysis (FBA) models have been developed which consider either extracellular fluxes or intracellular fluxes, respectively. In an at-tempt to predict both intracellular and extracellular fluxes, structured models have been introduced, but existing structured models compartmentalize pathways and do not con-sider the metabolic networks in detail. In this paper, we present a model-based optimiza-tion approach for the production of recombinant proteins in P. pastoris. Our approach is based on dynamic flux balance analysis (dFBA) and elementary process functions (EPF). We show that our concept is able to predict both dynamic extracellular concentrations and time-dependent intracellular fluxes in detail with no need for compartmentalization. We also present an efficient solution strategy for our approach.},
	booktitle = {Computer {Aided} {Chemical} {Engineering}},
	author = {Emenike, Victor N. and Schulze, Moritz and Schenkendorf, René and Krewer, Ulrike},
	year = {2017},
	doi = {10.1016/B978-0-444-63965-3.50471-2},
	keywords = {Pichia pastoris, biopharmaceutical manufacturing, bioreactor design, dynamic flux balance analysis, elementary process functions, optimization},
	pages = {2815--2820},
}

Pichia pastoris is an important host cell for the heterologous expression of recombinant proteins. In order to understand and design optimal biopharmaceutical processes with P. pastoris, unstructured and flux balance analysis (FBA) models have been developed which consider either extracellular fluxes or intracellular fluxes, respectively. In an at-tempt to predict both intracellular and extracellular fluxes, structured models have been introduced, but existing structured models compartmentalize pathways and do not con-sider the metabolic networks in detail. In this paper, we present a model-based optimiza-tion approach for the production of recombinant proteins in P. pastoris. Our approach is based on dynamic flux balance analysis (dFBA) and elementary process functions (EPF). We show that our concept is able to predict both dynamic extracellular concentrations and time-dependent intracellular fluxes in detail with no need for compartmentalization. We also present an efficient solution strategy for our approach.

@article{roder_multi-scale_2017,
	title = {Multi-{Scale} {Simulation} of {Heterogeneous} {Surface} {Film} {Growth} {Mechanisms} in {Lithium}-{Ion} {Batteries}},
	volume = {164},
	copyright = {All rights reserved},
	issn = {0013-4651},
	url = {http://jes.ecsdl.org/lookup/doi/10.1149/2.0241711jes},
	doi = {10.1149/2.0241711jes},
	abstract = {A quantitative description of the formation process of the solid electrolyte interface (SEI) on graphite electrodes requires the description of heterogeneous surface film growth mechanisms and continuum models. This article presents such an approach, which uses multi-scale modeling techniques to investigate multi-scale effects of the surface film growth. The model dynamically couples a macroscopic battery model with a kinetic Monte Carlo algorithm. The latter allows the study of atomistic surface reactions and heterogeneous surface film growth. The capability of this model is illustrated on an example using the common ethylene carbonate-based electrolyte in contact with a graphite electrode that features different particle radii. In this model, the atomistic configuration of the surface film structure impacts reactivity of the surface and thus the macroscopic reaction balances. The macroscopic properties impact surface current densities and overpotentials and thus surface film growth. The potential slope and charge consumption in graphite electrodes during the formation process qualitatively agrees with reported experimental results.},
	number = {11},
	journal = {Journal of The Electrochemical Society},
	author = {Röder, Fridolin and Braatz, Richard D. and Krewer, Ulrike},
	year = {2017},
	pages = {E3335--E3344},
}

A quantitative description of the formation process of the solid electrolyte interface (SEI) on graphite electrodes requires the description of heterogeneous surface film growth mechanisms and continuum models. This article presents such an approach, which uses multi-scale modeling techniques to investigate multi-scale effects of the surface film growth. The model dynamically couples a macroscopic battery model with a kinetic Monte Carlo algorithm. The latter allows the study of atomistic surface reactions and heterogeneous surface film growth. The capability of this model is illustrated on an example using the common ethylene carbonate-based electrolyte in contact with a graphite electrode that features different particle radii. In this model, the atomistic configuration of the surface film structure impacts reactivity of the surface and thus the macroscopic reaction balances. The macroscopic properties impact surface current densities and overpotentials and thus surface film growth. The potential slope and charge consumption in graphite electrodes during the formation process qualitatively agrees with reported experimental results.

@article{viandier_degradation_2016,
	title = {Degradation analysis of fibre-metal laminates under service conditions to predict their durability},
	volume = {1},
	copyright = {All rights reserved},
	url = {https://hal.archives-ouvertes.fr/hal-01839882/},
	abstract = {Fibre-Metal Laminate (FML) is an advanced material expected to possess improved mechanical properties than its sole constituents. Yet, only few studies focus on its durability. Thus, the aim of this study is to analyse the corrosion behaviour of FMLs based on carbon fibre composite (CFRP) and stainless steel (SST) in a sodium chloride solution. To fulfil this purpose, potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS) were utilized. It has been observed that, as FML, the carbon composite and the stainless steel would effectively form a galvanic cell that facilitates the composite acting as a cathode and the stainless steel as an anode. Moreover, galvanic corrosion is accompanied by pitting corrosion of the stainless steel electrode. Also the impedance data recorded can quantify the polarisation resistance of the materials, whereas the polarisation technique is more appropriate to measure the galvanic couple current density and the couple potential of a CFRP/stainless-steel-hybrid laminate. Accordingly, carrying out both electrochemical methods is a powerful approach to predict the galvanic corrosion behaviour of FMLs under service.},
	number = {1},
	journal = {Bulletin of the University Politehnica of Bucharest, Series D – Mechanical Engineering},
	author = {Viandier, Aurélie and Cramer, Jonathan and Stefaniak, Daniel and Schröder, Daniel and Krewer, Ulrike and Hühne, Christian and Sinapius, Michael},
	year = {2016},
	keywords = {CFRP, ELECTROCHEMICAL METHODS, FIBRE-METAL LAMINATES, IMPEDANCE SPECTROSCOPY, POTENTIODYNAMIC POLARISATION, STAINLESS STEEL},
}

Fibre-Metal Laminate (FML) is an advanced material expected to possess improved mechanical properties than its sole constituents. Yet, only few studies focus on its durability. Thus, the aim of this study is to analyse the corrosion behaviour of FMLs based on carbon fibre composite (CFRP) and stainless steel (SST) in a sodium chloride solution. To fulfil this purpose, potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS) were utilized. It has been observed that, as FML, the carbon composite and the stainless steel would effectively form a galvanic cell that facilitates the composite acting as a cathode and the stainless steel as an anode. Moreover, galvanic corrosion is accompanied by pitting corrosion of the stainless steel electrode. Also the impedance data recorded can quantify the polarisation resistance of the materials, whereas the polarisation technique is more appropriate to measure the galvanic couple current density and the couple potential of a CFRP/stainless-steel-hybrid laminate. Accordingly, carrying out both electrochemical methods is a powerful approach to predict the galvanic corrosion behaviour of FMLs under service.

@article{weinzierl_model-based_2016,
	title = {Model-based analysis of water management at anode of alkaline direct methanol fuel cells},
	volume = {143},
	copyright = {All rights reserved},
	issn = {00092509},
	url = {http://linkinghub.elsevier.com/retrieve/pii/S0009250915007836},
	doi = {10.1016/j.ces.2015.12.006},
	abstract = {Alkaline direct methanol fuel cells (ADMFCs) produce water at the aqueous fed anode. This complicates water management at anode which is analysed in this study by modelling three extreme case scenarios assuming different conditions for water transport or removal. All scenarios include recycling of methanol solution at anode outlet to achieve high methanol efficiencies. One scenario reveals that high operation times and high methanol efficiencies necessitate active stabilisation of anodic water level since both water accumulation and depletion can take place depending on operation conditions. Another scenario shows that water level can be stabilised by adjusting cathodic evaporation and the corresponding water removal from the system. The results indicate that feeding cathode with water-saturated gas is detrimental for stabilising water level. The last scenario suggests the addition of a gas flow to anodic outlet to remove excess water for water level stabilisation. Minimization of additional methanol loss requires to reach high humidities by evaporation. The present paper reveals the impact of processes occurring in ADMFCs on anodic water management and indicates the necessity to quantify water transport through membrane. Knowledge of the influence of operation conditions on water level in the anodic loop are beneficial for design of ADMFC systems.},
	journal = {Chemical Engineering Science},
	author = {Weinzierl, C. and Krewer, U.},
	month = apr,
	year = {2016},
	keywords = {ADMFC, Alkaline fuel cell, Anion exchange membrane, Fuel cell system, Mathematical modelling, Water management},
	pages = {181--193},
}

Alkaline direct methanol fuel cells (ADMFCs) produce water at the aqueous fed anode. This complicates water management at anode which is analysed in this study by modelling three extreme case scenarios assuming different conditions for water transport or removal. All scenarios include recycling of methanol solution at anode outlet to achieve high methanol efficiencies. One scenario reveals that high operation times and high methanol efficiencies necessitate active stabilisation of anodic water level since both water accumulation and depletion can take place depending on operation conditions. Another scenario shows that water level can be stabilised by adjusting cathodic evaporation and the corresponding water removal from the system. The results indicate that feeding cathode with water-saturated gas is detrimental for stabilising water level. The last scenario suggests the addition of a gas flow to anodic outlet to remove excess water for water level stabilisation. Minimization of additional methanol loss requires to reach high humidities by evaporation. The present paper reveals the impact of processes occurring in ADMFCs on anodic water management and indicates the necessity to quantify water transport through membrane. Knowledge of the influence of operation conditions on water level in the anodic loop are beneficial for design of ADMFC systems.

@article{schroder_numerical_2016,
	title = {Numerical simulation of gas-diffusion-electrodes with moving gas-liquid interface: {A} study on pulse-current operation and electrode flooding},
	volume = {84},
	copyright = {All rights reserved},
	issn = {00981354},
	url = {http://linkinghub.elsevier.com/retrieve/pii/S0098135415003002},
	doi = {10.1016/j.compchemeng.2015.09.005},
	abstract = {In gas-diffusion-electrodes of electrochemical systems, the interface between gas and liquid electrolyte can move with operation time. It is challenging to mathematically assess moving interfaces, especially if the transient and spatial distribution of species are of interest. We mathematically model a gas-diffusion-electrode and apply a finite volume method with moving grid to solve the model equations. The step-size of the finite volume method is coupled to the moving gas-liquid interface, which is coupled to the current density applied. In detail, we study pulse-current operation and flooding of the electrode, and investigate parameters that influence the oxygen distribution in the electrode. The results obtained emphasize the benefit of the moving grid method applied. This method is able to assess the accurate diffusion resistance for oxygen in the gas-diffusion-electrode. Based on this work, possible limitations of gas-diffusion-electrodes can be derived for their usage in metal air batteries.},
	journal = {Computers and Chemical Engineering},
	author = {Schröder, Daniel and Laue, Vincent and Krewer, Ulrike},
	month = jan,
	year = {2016},
	keywords = {Finite volume method, Gas-diffusion-electrode, Mathematical model, Metal air battery, Moving grid, Zinc air battery},
	pages = {217--225},
}

In gas-diffusion-electrodes of electrochemical systems, the interface between gas and liquid electrolyte can move with operation time. It is challenging to mathematically assess moving interfaces, especially if the transient and spatial distribution of species are of interest. We mathematically model a gas-diffusion-electrode and apply a finite volume method with moving grid to solve the model equations. The step-size of the finite volume method is coupled to the moving gas-liquid interface, which is coupled to the current density applied. In detail, we study pulse-current operation and flooding of the electrode, and investigate parameters that influence the oxygen distribution in the electrode. The results obtained emphasize the benefit of the moving grid method applied. This method is able to assess the accurate diffusion resistance for oxygen in the gas-diffusion-electrode. Based on this work, possible limitations of gas-diffusion-electrodes can be derived for their usage in metal air batteries.

@article{roder_simulating_2016,
	title = {Simulating the {Impact} of {Particle} {Size} {Distribution} on the {Performance} of {Graphite} {Electrodes} in {Lithium}-{Ion} {Batteries}},
	volume = {4},
	copyright = {All rights reserved},
	issn = {21944296},
	url = {http://doi.wiley.com/10.1002/ente.201600232},
	doi = {10.1002/ente.201600232},
	abstract = {In this work we present a fundamental model-based analysis of the effect of active material particle size distribution (PSD) on graphite electrodes and their performance. We fo- cused on the determination of the impact of differently shaped and scaled PSDs on the electrode performance, which is mainly influenced by the performance of the indi- vidual particles and their interaction. A mathematical elec- trode model with a distributed particle size is used for analy- sis to identify the different local current densities and the charging behavior of the particles. The heterogeneity pro- vokes uneven surface overpotentials and reaction rates. Their identification facilitates the investigation of the degra- dation of such heterogeneous systems. In addition, we pres- ent an approach that accounts for the change of a PSD be- cause of the restructuring of the electrode morphology during battery usage into the mathematical model and identi- fy the general impact of particle cracking and agglomeration on the battery performance. Moreover, the importance of PSD in Li-ion batteries is shown by comparing the results obtained with a single particle model used commonly. This comparison shows that in case of narrow distributions sur- face-area- and volume-based mean approximations are suffi- cient to predict overpotentials and electrode capacity if ki- netic losses are dominated either by reaction at the surface or diffusion processes, respectively. This work indicates that the PSD and its change impact the performance and degra- dation of Li-ion batteries considerably. We suggest that the PSD and its evolution should be of particular interest in the study of the degradation of particle-based electrodes.},
	number = {12},
	journal = {Energy Technology},
	author = {Röder, Fridolin and Sonntag, Sören and Schröder, Daniel and Krewer, Ulrike},
	year = {2016},
	keywords = {batteries, electrochemistry, electrodes, graphite, particle size distribution{\textbackslash}textbackslashtextbackslashtextless},
	pages = {1588--1597},
}

In this work we present a fundamental model-based analysis of the effect of active material particle size distribution (PSD) on graphite electrodes and their performance. We fo- cused on the determination of the impact of differently shaped and scaled PSDs on the electrode performance, which is mainly influenced by the performance of the indi- vidual particles and their interaction. A mathematical elec- trode model with a distributed particle size is used for analy- sis to identify the different local current densities and the charging behavior of the particles. The heterogeneity pro- vokes uneven surface overpotentials and reaction rates. Their identification facilitates the investigation of the degra- dation of such heterogeneous systems. In addition, we pres- ent an approach that accounts for the change of a PSD be- cause of the restructuring of the electrode morphology during battery usage into the mathematical model and identi- fy the general impact of particle cracking and agglomeration on the battery performance. Moreover, the importance of PSD in Li-ion batteries is shown by comparing the results obtained with a single particle model used commonly. This comparison shows that in case of narrow distributions sur- face-area- and volume-based mean approximations are suffi- cient to predict overpotentials and electrode capacity if ki- netic losses are dominated either by reaction at the surface or diffusion processes, respectively. This work indicates that the PSD and its change impact the performance and degra- dation of Li-ion batteries considerably. We suggest that the PSD and its evolution should be of particular interest in the study of the degradation of particle-based electrodes.

@incollection{roder_multi-scale_2016,
	title = {Multi-{Scale} {Modeling} of {Solid} {Electrolyte} {Interface} {Formation} in {Lithium}-{Ion} {Batteries}},
	volume = {38},
	copyright = {All rights reserved},
	isbn = {978-0-444-63428-3},
	url = {http://linkinghub.elsevier.com/retrieve/pii/B978044463428350031X},
	abstract = {This article presents a multi-scale model to simulate and analyze the formation of Solid Electrolyte Interface (SEI). A macroscopic model of battery and SEI is coupled with an atomistic kinetic Monte Carlo model for surface reactions. The developed multi-scale algorithm allows numerical simulation of key degradation mechanisms over long time and length scales. As a practical example, a full discharge process is simulated. The results show data exchange between stochastic and deterministic model as well as exemplary effects of reaction mechanisms on layer structure and battery performance. This novel approach enables simulations and detailed studies of complex SEI layer formation processes.},
	booktitle = {Computer {Aided} {Chemical} {Engineering}},
	author = {Röder, Fridolin and Braatz, Richard D. and Krewer, Ulrike},
	year = {2016},
	doi = {10.1016/B978-0-444-63428-3.50031-X},
	keywords = {Degradation, Lithium-Ion Battery, Multi-Scale Modeling},
	pages = {157--162},
}

This article presents a multi-scale model to simulate and analyze the formation of Solid Electrolyte Interface (SEI). A macroscopic model of battery and SEI is coupled with an atomistic kinetic Monte Carlo model for surface reactions. The developed multi-scale algorithm allows numerical simulation of key degradation mechanisms over long time and length scales. As a practical example, a full discharge process is simulated. The results show data exchange between stochastic and deterministic model as well as exemplary effects of reaction mechanisms on layer structure and battery performance. This novel approach enables simulations and detailed studies of complex SEI layer formation processes.

@article{emenike_model-based_2016,
	title = {Model-{Based} {Optimal} {Design} of {Continuous}-{Flow} {Reactors} for the {Synthesis} of {Active} {Pharmaceutical} {Ingredients}},
	volume = {88},
	copyright = {All rights reserved},
	issn = {15222640},
	url = {http://doi.wiley.com/10.1002/cite.201650267},
	doi = {10.1002/cite.201650267},
	number = {9},
	journal = {Chemie-Ingenieur-Technik},
	author = {Emenike, V. N. and Krewer, U.},
	month = sep,
	year = {2016},
	pages = {1215--1216},
}

@inproceedings{schenkendorf_supporting_2016,
	title = {Supporting the shift towards continuous pharmaceutical manufacturing by condition monitoring},
	volume = {2016-Novem},
	copyright = {All rights reserved},
	isbn = {978-1-5090-0658-8},
	url = {http://ieeexplore.ieee.org/document/7739813/},
	doi = {10.1109/SYSTOL.2016.7739813},
	abstract = {© 2016 IEEE.Over the last decade there has been an increased interest in the pharmaceutical industry to shift the manufacturing process of drugs from batch to continuous operation. The continuous manufacturing of pharmaceuticals provides significant benefits, e.g. savings in cost, time and materials - to name but a few. The implementation of a continuous manufacturing strategy, however, is challenging. To gain profit from a continuous process one has to ensure its proper operation, i.e. a long time-span until the next prospective unscheduled downtime. Thus, the installed operation units have to be: 1) robust against disturbances by engineering design principles and by advanced fault tolerant control schemes, respectively; and 2) the condition of the operation units has to be monitored reliably to trigger, in case of need, appropriate intervention strategies in a timely manner. In this paper, the focus is on the monitoring aspect. Here, a model-based fault detection and identification framework is implemented, which selects the most data-supported model candidate from a set of predefined model hypotheses including the reference model (normal behavior) as well as failure models. In addition, to enable an improved diagnosis the system under study can be steered deliberately based on the proposed concept resulting into an active fault diagnosis framework. Preliminary results are demonstrated by an academic three-tank system.},
	booktitle = {Conference on {Control} and {Fault}-{Tolerant} {Systems}, {SysTol}},
	publisher = {IEEE},
	author = {Schenkendorf, Rene},
	month = sep,
	year = {2016},
	pages = {593--598},
}

© 2016 IEEE.Over the last decade there has been an increased interest in the pharmaceutical industry to shift the manufacturing process of drugs from batch to continuous operation. The continuous manufacturing of pharmaceuticals provides significant benefits, e.g. savings in cost, time and materials - to name but a few. The implementation of a continuous manufacturing strategy, however, is challenging. To gain profit from a continuous process one has to ensure its proper operation, i.e. a long time-span until the next prospective unscheduled downtime. Thus, the installed operation units have to be: 1) robust against disturbances by engineering design principles and by advanced fault tolerant control schemes, respectively; and 2) the condition of the operation units has to be monitored reliably to trigger, in case of need, appropriate intervention strategies in a timely manner. In this paper, the focus is on the monitoring aspect. Here, a model-based fault detection and identification framework is implemented, which selects the most data-supported model candidate from a set of predefined model hypotheses including the reference model (normal behavior) as well as failure models. In addition, to enable an improved diagnosis the system under study can be steered deliberately based on the proposed concept resulting into an active fault diagnosis framework. Preliminary results are demonstrated by an academic three-tank system.

@article{kubannek_cyclone_2016,
	title = {A {Cyclone} {Flow} {Cell} for {Quantitative} {Analysis} of {Kinetics} at {Porous} {Electrodes} by {Differential} {Electrochemical} {Mass} {Spectrometry}},
	volume = {210},
	copyright = {All rights reserved},
	issn = {00134686},
	doi = {10.1016/j.electacta.2016.05.212},
	abstract = {In this work the scope of differential electrochemical mass spectrometry (DEMS) is extended towards quantitatively identifying kinetics of electrochemical reactions in porous electrodes by dynamic measurements. The method is demonstrated by analyzing the kinetics of CO oxidation on a carbon supported Pt/Ru catalyst using a cyclone flow DEMS cell, which allows online studies of porous electrodes. The cyclone flow cell generates a rotating flow field above the stationary electrode. Experimentally validated CFD simulations show that the constructed cell features a homogeneous concentration boundary layer over approximately 75\% of the electrode surface area, and that the diffusion limited current density is proportional to flow rate to the power of two third, which is characteristic for turbulent flows. Calibration experiments are performed, and a physical model including mass transfer and reactions inside the porous electrode as well as information about the concentration boundary layer from the CFD results is set up. By matching simulation results and experimental data for CO oxidation, kinetic parameters are determined. With DEMS, not only current and potential but also the CO2production rate can be observed with a high time resolution which allows to conduct quantitative macrokinetic analysis and to identify parameters quite reliably with a low number of dynamic experiments.},
	journal = {Electrochimica Acta},
	author = {Kubannek, F. and Krewer, U.},
	year = {2016},
	keywords = {CO oxidation, Cyclone flow, Differential Electrochemical Mass Spectrometry (DE, Porous electrodes, Reaction kinetics},
	pages = {862--873},
}

In this work the scope of differential electrochemical mass spectrometry (DEMS) is extended towards quantitatively identifying kinetics of electrochemical reactions in porous electrodes by dynamic measurements. The method is demonstrated by analyzing the kinetics of CO oxidation on a carbon supported Pt/Ru catalyst using a cyclone flow DEMS cell, which allows online studies of porous electrodes. The cyclone flow cell generates a rotating flow field above the stationary electrode. Experimentally validated CFD simulations show that the constructed cell features a homogeneous concentration boundary layer over approximately 75% of the electrode surface area, and that the diffusion limited current density is proportional to flow rate to the power of two third, which is characteristic for turbulent flows. Calibration experiments are performed, and a physical model including mass transfer and reactions inside the porous electrode as well as information about the concentration boundary layer from the CFD results is set up. By matching simulation results and experimental data for CO oxidation, kinetic parameters are determined. With DEMS, not only current and potential but also the CO2production rate can be observed with a high time resolution which allows to conduct quantitative macrokinetic analysis and to identify parameters quite reliably with a low number of dynamic experiments.

@article{jenssen_anode_2015,
	title = {Anode flooding characteristics as design boundary for a hydrogen supply system for automotive polymer electrolyte membrane fuel cells},
	volume = {298},
	copyright = {All rights reserved},
	issn = {03787753},
	url = {http://linkinghub.elsevier.com/retrieve/pii/S0378775315301609},
	doi = {10.1016/j.jpowsour.2015.08.005},
	abstract = {An automotive fuel cell is investigated to define the design boundaries for an automotive hydrogen supply system with regard to anode flooding. The flooding characteristics of the fuel cell anode at various operating conditions (hydrogen flow rate, pressure, temperature, current density) are analyzed by in-situ and ex-situ measurements. Stable operation conditions are identified and a relation to the operating conditions is established. For adequate water removal, a minimum Reynolds number in the gas channels has to be adjusted. Using this information, different hydrogen supply system designs are compared in their compliance with the stability requirements. It is shown that passive hydrogen supply systems do not achieve all fuel cell requirements regarding power density, lifetime and robustness.},
	journal = {Journal of Power Sources},
	author = {Jenssen, Dirk and Berger, Oliver and Krewer, Ulrike},
	year = {2015},
	keywords = {Anode water management, Automotive hydrogen supply system, Design process, Water removal},
	pages = {249--258},
}

An automotive fuel cell is investigated to define the design boundaries for an automotive hydrogen supply system with regard to anode flooding. The flooding characteristics of the fuel cell anode at various operating conditions (hydrogen flow rate, pressure, temperature, current density) are analyzed by in-situ and ex-situ measurements. Stable operation conditions are identified and a relation to the operating conditions is established. For adequate water removal, a minimum Reynolds number in the gas channels has to be adjusted. Using this information, different hydrogen supply system designs are compared in their compliance with the stability requirements. It is shown that passive hydrogen supply systems do not achieve all fuel cell requirements regarding power density, lifetime and robustness.

@article{khadke_performance_2015,
	title = {Performance losses at {H2}/{O2alkaline} membrane fuel cell},
	volume = {51},
	copyright = {All rights reserved},
	issn = {13882481},
	url = {http://linkinghub.elsevier.com/retrieve/pii/S1388248114003774},
	doi = {10.1016/j.elecom.2014.12.006},
	abstract = {H2/O2alkaline membrane fuel cell (AMFC) is evaluated by polarization curves and conductivity measurements to determine the performance limiting factors. The analysis of IR corrected polarization curves shows that at medium to high current region significant potential loss in AMFC is caused by low ionic conductivity of membrane and catalyst layer, and limitations from mass transport of water. In low to medium current region the severe performance loss is caused by low water concentration at catalyst surface due to insufficient water concentration in the fully humidified oxidant at ≤ 60°C.},
	journal = {Electrochemistry Communications},
	author = {Khadke, Prashant Subhas and Krewer, Ulrike},
	month = feb,
	year = {2015},
	keywords = {Alkaline membrane fuel cell, Catalyst layer resistance, Water concentration, Water transport},
	pages = {117--120},
}

H2/O2alkaline membrane fuel cell (AMFC) is evaluated by polarization curves and conductivity measurements to determine the performance limiting factors. The analysis of IR corrected polarization curves shows that at medium to high current region significant potential loss in AMFC is caused by low ionic conductivity of membrane and catalyst layer, and limitations from mass transport of water. In low to medium current region the severe performance loss is caused by low water concentration at catalyst surface due to insufficient water concentration in the fully humidified oxidant at ≤ 60°C.

@inproceedings{zenith_optimal_2015,
	title = {Optimal concentration control for direct methanol fuel cells},
	volume = {28},
	copyright = {All rights reserved},
	doi = {10.1016/j.ifacol.2015.09.054},
	abstract = {Two modifications to a reference direct methanol fuel-cell (DMFC) system are considered to improve methanol fuel utilisation. Fuel utilisation can be optimised by minimising the parasitic methanol crossover by manipulating methanol concentration in the fuel cells. Simulations of the two systems indicate that there is considerable potential to increase fuel utilisation for dynamic concentration controLin DMFC systems subject to variable load.},
	booktitle = {{IFAC}-{PapersOnLine}},
	author = {Zenith, Federico and Na, Youngseung and Krewer, Ulrike},
	year = {2015},
	keywords = {DMFC, Dynamics, Efficiency, Feedback, Feedforward, Fuel cell, MIMO, Methanol, Simulation},
	pages = {722--727},
}

Two modifications to a reference direct methanol fuel-cell (DMFC) system are considered to improve methanol fuel utilisation. Fuel utilisation can be optimised by minimising the parasitic methanol crossover by manipulating methanol concentration in the fuel cells. Simulations of the two systems indicate that there is considerable potential to increase fuel utilisation for dynamic concentration controLin DMFC systems subject to variable load.

@article{na_increasing_2015,
	title = {Increasing fuel efficiency of direct methanol fuel cell systems with feedforward control of the operating concentration},
	volume = {8},
	copyright = {All rights reserved},
	issn = {19961073},
	url = {http://www.mdpi.com/1996-1073/8/9/10409},
	doi = {10.3390/en80910409},
	abstract = {Most of the R\&D on fuel cells for portable applications concentrates on increasing efficiencies and energy densities to compete with other energy storage devices, especially batteries. To improve the efficiency of direct methanol fuel cell (DMFC) systems, several modifications to system layouts and operating strategies are considered in this paper, rather than modifications to the fuel cell itself. Two modified DMFC systems are presented, one with an additional inline mixer and a further modification of it with a separate tank to recover condensed water. The set point for methanol concentration control in the solution is determined by fuel efficiency and varies with the current and other process variables. Feedforward concentration control enables variable concentration for dynamic loads. Simulation results were validated experimentally with fuel cell systems.},
	number = {9},
	journal = {Energies},
	author = {Na, Youngseung and Zenith, Federico and Krewer, Ulrike},
	month = sep,
	year = {2015},
	keywords = {Concentration, Control, Fuel cell system},
	pages = {10409--10429},
}

Most of the R&D on fuel cells for portable applications concentrates on increasing efficiencies and energy densities to compete with other energy storage devices, especially batteries. To improve the efficiency of direct methanol fuel cell (DMFC) systems, several modifications to system layouts and operating strategies are considered in this paper, rather than modifications to the fuel cell itself. Two modified DMFC systems are presented, one with an additional inline mixer and a further modification of it with a separate tank to recover condensed water. The set point for methanol concentration control in the solution is determined by fuel efficiency and varies with the current and other process variables. Feedforward concentration control enables variable concentration for dynamic loads. Simulation results were validated experimentally with fuel cell systems.

@article{schroder_performance_2015,
	title = {Performance of zinc air batteries with added {K2CO3} in the alkaline electrolyte},
	volume = {45},
	copyright = {All rights reserved},
	issn = {15728838},
	url = {http://link.springer.com/10.1007/s10800-015-0817-0},
	doi = {10.1007/s10800-015-0817-0},
	abstract = {© 2015, Springer Science+Business Media Dordrecht. Intentionally adding potassium carbonate to the high molar alkaline electrolyte is one possibility to mitigate the negative impact of carbonation in zinc air batteries (ZABs) that were investigated in this novel study. In this work, an experimental analysis of the electrochemical performance of ZABs with added potassium carbonate in potassium hydroxide electrolyte was conducted. The experiments included polarization curve measurements, electrochemical impedance spectroscopy measurements, and constant current discharge with an in-house battery set-up. In addition, ionic conductivity was measured for mixtures of potassium hydroxide and potassium carbonate solutions. The results implied that up to 50 mol\% of added potassium carbonate in the electrolyte had a weaker influence on the cell performance than a decreased amount of hydroxide ions in the electrolyte from 21.9 to 1.8 mol\%. However, discharge measurements showed that the cell potential and the maximum state-of-discharge are decreased for the operation with 50.00 mol\% of added potassium carbonate. The conductivity measurements revealed that solutions with (Formula presented.) and added potassium carbonate possessed similar ionic conductivity, when compared to the standard 6 M KOH electrolyte. All in all, the analysis showed that it was acceptable to add potassium carbonate to the high molar potassium hydroxide electrolyte, while still obtaining stable cell potential under the premise to increase the practical energy density and the long-term stability of zinc air batteries. The here presented findings might help to establish the zinc air battery as next generation type battery.},
	number = {5},
	journal = {Journal of Applied Electrochemistry},
	author = {Schröder, Daniel and Sinai Borker, Neeraj Nitin and König, Michael and Krewer, Ulrike},
	year = {2015},
	keywords = {Discharge performance, Electrolyte composition, Impedance spectroscopy, Potassium carbonate, Potassium hydroxide, Zinc air battery},
	pages = {427--437},
}

© 2015, Springer Science+Business Media Dordrecht. Intentionally adding potassium carbonate to the high molar alkaline electrolyte is one possibility to mitigate the negative impact of carbonation in zinc air batteries (ZABs) that were investigated in this novel study. In this work, an experimental analysis of the electrochemical performance of ZABs with added potassium carbonate in potassium hydroxide electrolyte was conducted. The experiments included polarization curve measurements, electrochemical impedance spectroscopy measurements, and constant current discharge with an in-house battery set-up. In addition, ionic conductivity was measured for mixtures of potassium hydroxide and potassium carbonate solutions. The results implied that up to 50 mol% of added potassium carbonate in the electrolyte had a weaker influence on the cell performance than a decreased amount of hydroxide ions in the electrolyte from 21.9 to 1.8 mol%. However, discharge measurements showed that the cell potential and the maximum state-of-discharge are decreased for the operation with 50.00 mol% of added potassium carbonate. The conductivity measurements revealed that solutions with (Formula presented.) and added potassium carbonate possessed similar ionic conductivity, when compared to the standard 6 M KOH electrolyte. All in all, the analysis showed that it was acceptable to add potassium carbonate to the high molar potassium hydroxide electrolyte, while still obtaining stable cell potential under the premise to increase the practical energy density and the long-term stability of zinc air batteries. The here presented findings might help to establish the zinc air battery as next generation type battery.

@inproceedings{torchio_real-time_2015,
	title = {Real-time model predictive control for the optimal charging of a lithium-ion battery},
	volume = {2015-July},
	copyright = {All rights reserved},
	isbn = {978-1-4799-8684-2},
	doi = {10.1109/ACC.2015.7172043},
	abstract = {© 2015 American Automatic Control Council.Li-ion batteries are widely used in industrial applications due to their high energy density, slow material degradation, and low self-discharge. The existing advanced battery management systems (ABMs) in industry employ semiempirical battery models that do not use first-principles understanding to relate battery operation to the relevant physical constraints, which results in conservative battery charging protocols. This article proposes a Quadratic Dynamic Matrix Control (QDMC) approach to minimize the charge time of batteries to reach a desired state of charge (SOC) while taking temperature and voltage constraints into account. This algorithm is based on an input-output model constructed from a first-principles electrochemical battery model known in the literature as the pseudo two-dimensional (P2D) model. In simulations, this approach is shown to significantly reduce charging time.},
	booktitle = {Proceedings of the {American} {Control} {Conference}},
	author = {Torchio, Marcello and Wolff, Nicolas A. and Raimondo, Davide M. and Magni, Lalo and Krewer, Ulrike and Gopaluni, R. Bushan and Paulson, Joel A. and Braatz, Richard D.},
	year = {2015},
	pages = {4536--4541},
}

© 2015 American Automatic Control Council.Li-ion batteries are widely used in industrial applications due to their high energy density, slow material degradation, and low self-discharge. The existing advanced battery management systems (ABMs) in industry employ semiempirical battery models that do not use first-principles understanding to relate battery operation to the relevant physical constraints, which results in conservative battery charging protocols. This article proposes a Quadratic Dynamic Matrix Control (QDMC) approach to minimize the charge time of batteries to reach a desired state of charge (SOC) while taking temperature and voltage constraints into account. This algorithm is based on an input-output model constructed from a first-principles electrochemical battery model known in the literature as the pseudo two-dimensional (P2D) model. In simulations, this approach is shown to significantly reduce charging time.

@article{schroder_model_2014,
	title = {Model based quantification of air-composition impact on secondary zinc air batteries},
	volume = {117},
	copyright = {All rights reserved},
	issn = {00134686},
	doi = {10.1016/j.electacta.2013.11.116},
	abstract = {In this work we present an isothermal mathematical model of a secondary zinc air battery with alkaline liquid electrolyte. The model approach is flexible and allows to analyze the impact of surrounding air composition with its relative humidity, carbon dioxide and oxygen content on battery operation. We thereby apply an idealized approach to explore general limitations which give useful predictions for practical zinc air battery operation. Galvanostatic charge and discharge simulations show that air composition strongly impacts zinc air battery operation. Water level at anode and cathode, species concentrations and cell potential are shown to vary with air-composition impact during operation and may reach critical values which reduce battery lifetime. In detail, we deduce that intermediate relative humidity values of approximately 65\%, carbon dioxide concentrations below 10 ppm and pure oxygen are beneficial for high performance and long term stable zinc air battery operation at 298 K with 6M potassium hydroxide as alkaline liquid electrolyte. The presented results will give useful information on operating strategies for zinc air batteries and electrochemical energy storage systems with open air electrode. The model might be adapted for other metal air batteries with aqueous electrolyte. © 2013 Elsevier Ltd.},
	journal = {Electrochimica Acta},
	author = {Schröder, Daniel and Krewer, Ulrike},
	year = {2014},
	keywords = {Carbon dioxide, Humidity, Mathematical modeling, Oxygen, Potassium hydroxide, Secondary zinc air battery},
	pages = {541--553},
}

In this work we present an isothermal mathematical model of a secondary zinc air battery with alkaline liquid electrolyte. The model approach is flexible and allows to analyze the impact of surrounding air composition with its relative humidity, carbon dioxide and oxygen content on battery operation. We thereby apply an idealized approach to explore general limitations which give useful predictions for practical zinc air battery operation. Galvanostatic charge and discharge simulations show that air composition strongly impacts zinc air battery operation. Water level at anode and cathode, species concentrations and cell potential are shown to vary with air-composition impact during operation and may reach critical values which reduce battery lifetime. In detail, we deduce that intermediate relative humidity values of approximately 65%, carbon dioxide concentrations below 10 ppm and pure oxygen are beneficial for high performance and long term stable zinc air battery operation at 298 K with 6M potassium hydroxide as alkaline liquid electrolyte. The presented results will give useful information on operating strategies for zinc air batteries and electrochemical energy storage systems with open air electrode. The model might be adapted for other metal air batteries with aqueous electrolyte. © 2013 Elsevier Ltd.

@article{schroder_analyzing_2014,
	title = {Analyzing transport paths in the air electrode of a zinc air battery using {X}-ray tomography},
	volume = {40},
	copyright = {All rights reserved},
	issn = {13882481},
	doi = {10.1016/j.elecom.2014.01.001},
	abstract = {X-ray tomography was used to investigate the discharge behavior of a zinc air battery in-operando. A special battery set-up and preparation was used in order to meet both electrochemical and tomographic requirements. The prepared battery was discharged galvanostatically and analyzed with tomographic measurements at a state of charge of 100\%, 75\% and 65\%. End-of-life of the investigated zinc air battery is reached much earlier than the amount of active zinc particles would allow. This is attributed to an observable blockage of oxygen transport paths in the gas diffusion layer caused by increased flooding with liquid. © 2014 Elsevier B.V.},
	journal = {Electrochemistry Communications},
	author = {Schröder, Daniel and Arlt, Tobias and Krewer, Ulrike and Manke, Ingo},
	year = {2014},
	pmid = {25052830},
	keywords = {Air electrode, Gas diffusion layer, Imaging, Transport paths, X-ray tomography, Zinc air battery},
	pages = {88--91},
}

X-ray tomography was used to investigate the discharge behavior of a zinc air battery in-operando. A special battery set-up and preparation was used in order to meet both electrochemical and tomographic requirements. The prepared battery was discharged galvanostatically and analyzed with tomographic measurements at a state of charge of 100%, 75% and 65%. End-of-life of the investigated zinc air battery is reached much earlier than the amount of active zinc particles would allow. This is attributed to an observable blockage of oxygen transport paths in the gas diffusion layer caused by increased flooding with liquid. © 2014 Elsevier B.V.

@article{khadke_mass-transport_2014,
	title = {Mass-{Transport} characteristics of oxygen at pt/anion exchange ionomer interface},
	volume = {118},
	copyright = {All rights reserved},
	issn = {19327455},
	doi = {10.1021/jp5011549},
	abstract = {This work quantifies the mass transport characteristics of O2 at Pt/anion exchange ionomer by determining the solubility and diffusion coefficient of O2 in Tokuyama AS-4 anion exchange ionomer film. To determine these parameters electrochemical methods such as linear sweep voltammetry and chronoamperometry are performed on rotating disk electrode. The diffusion process in AS-4 ionomer film is found to be fickian in nature; i.e. it is shown that the diffusion coefficient is independent of concentration and film thickness by calculating the diffusion coefficient at various film thicknesses and rotation speed of electrode. In comparison to Nafion ionomer, the magnitude of diffusion coefficient in anion exchange ionomer is found to be one order higher and solubility is found to be one order lower. However the overall permeability, defined by product of diffusion coefficient and solubility is similar to that Nafion ionomer film. In addition, durability studies of anion exchange ionomer coated Pt disk shows electrochemical stability of anion ionomer in alkaline media. With these studies it is shown},
	number = {21},
	journal = {Journal of Physical Chemistry C},
	author = {Khadke, Prashant Subhas and Krewer, Ulrike},
	year = {2014},
	pages = {11215--11223},
}

This work quantifies the mass transport characteristics of O2 at Pt/anion exchange ionomer by determining the solubility and diffusion coefficient of O2 in Tokuyama AS-4 anion exchange ionomer film. To determine these parameters electrochemical methods such as linear sweep voltammetry and chronoamperometry are performed on rotating disk electrode. The diffusion process in AS-4 ionomer film is found to be fickian in nature; i.e. it is shown that the diffusion coefficient is independent of concentration and film thickness by calculating the diffusion coefficient at various film thicknesses and rotation speed of electrode. In comparison to Nafion ionomer, the magnitude of diffusion coefficient in anion exchange ionomer is found to be one order higher and solubility is found to be one order lower. However the overall permeability, defined by product of diffusion coefficient and solubility is similar to that Nafion ionomer film. In addition, durability studies of anion exchange ionomer coated Pt disk shows electrochemical stability of anion ionomer in alkaline media. With these studies it is shown

@article{kraus_model-based_2014,
	title = {Model-based analysis of anion-exchanger positioning in direct methanol fuel cell systems},
	volume = {262},
	copyright = {All rights reserved},
	issn = {03787753},
	doi = {10.1016/j.jpowsour.2014.03.068},
	abstract = {In this work we present a model based study to investigate the presence of anion exchangers in direct methanol fuel cell (DMFC) systems. It is well known that environmental or fuel impurities lead to accumulation of harmful anions, such as chloride, in the system. However, due to DMFC anodic reaction, a carbonate system is present. These corbanate anions have to be taken into account for the anion exchanger design and placement as well as for the system operation strategy with and without anion exchanger, which is the objective of this study. For this purpose, the expected amount of harmful chloride ions in a DMFC system is estimated, and that of carbonate ions is calculated with a model of the carbonate system in a DMFC system. The predicition of durability and dimensions of an anion exchanger is based on a monovalent anion exchange model. The design of gas liquid separators in the DMFC system has a major influence on the amount of dissolved carbon dioxide, which is crucial for durability and dimension of a system integrated anion exchanger. Finally, feasible positions of anion exchanger in a DMFC system are elaborated to fulfill the needs for long term and stable DMFC operation. © 2014 Elsevier B.V. All rights reserved.},
	journal = {Journal of Power Sources},
	author = {Kraus, Maik and Schröder, Daniel and Krewer, Ulrike},
	year = {2014},
	keywords = {Anion exchanger, DMFC, Ionic impurities, Modeling},
	pages = {364--371},
}

In this work we present a model based study to investigate the presence of anion exchangers in direct methanol fuel cell (DMFC) systems. It is well known that environmental or fuel impurities lead to accumulation of harmful anions, such as chloride, in the system. However, due to DMFC anodic reaction, a carbonate system is present. These corbanate anions have to be taken into account for the anion exchanger design and placement as well as for the system operation strategy with and without anion exchanger, which is the objective of this study. For this purpose, the expected amount of harmful chloride ions in a DMFC system is estimated, and that of carbonate ions is calculated with a model of the carbonate system in a DMFC system. The predicition of durability and dimensions of an anion exchanger is based on a monovalent anion exchange model. The design of gas liquid separators in the DMFC system has a major influence on the amount of dissolved carbon dioxide, which is crucial for durability and dimension of a system integrated anion exchanger. Finally, feasible positions of anion exchanger in a DMFC system are elaborated to fulfill the needs for long term and stable DMFC operation. © 2014 Elsevier B.V. All rights reserved.

@article{weinzierl_model-based_2014,
	title = {Model-based analysis of water management in alkaline direct methanol fuel cells},
	volume = {268},
	copyright = {All rights reserved},
	issn = {03787753},
	doi = {10.1016/j.jpowsour.2014.06.070},
	abstract = {Mathematical modelling is used to analyse water management in Alkaline Direct Methanol Fuel Cells (ADMFCs) with an anion exchange membrane as electrolyte. Cathodic water supply is identified as one of the main challenges and investigated at different operation conditions. Two extreme case scenarios are modelled to study the feasible conditions for sufficient water supply. Scenario 1 reveals that water supply by cathodic inlet is insufficient and, thus, water transport through membrane is essential for ADMFC operation. The second scenario is used to analyse requirements on water transport through the membrane for different operation conditions. These requirements are influenced by current density, evaporation rate, methanol cross-over and electro-osmotic drag of water. Simulations indicate that water supply is mainly challenging for high current densities and demands on high water diffusion are intensified by water drag. Thus, current density might be limited by water transport through membrane. The presented results help to identify important effects and processes in ADMFCs with a polymer electrolyte membrane and to understand these processes. Furthermore, the requirements identified by modelling show the importance of considering water transport through membrane besides conductivity and methanol cross-over especially for designing new membrane materials. © 2014 Elsevier B.V. All rights reserved.},
	journal = {Journal of Power Sources},
	author = {Weinzierl, C. and Krewer, U.},
	year = {2014},
	keywords = {Alkaline fuel cell, Anion exchange membrane, Mathematical modelling, Methanol, Water management, Water transport},
	pages = {911--921},
}

Mathematical modelling is used to analyse water management in Alkaline Direct Methanol Fuel Cells (ADMFCs) with an anion exchange membrane as electrolyte. Cathodic water supply is identified as one of the main challenges and investigated at different operation conditions. Two extreme case scenarios are modelled to study the feasible conditions for sufficient water supply. Scenario 1 reveals that water supply by cathodic inlet is insufficient and, thus, water transport through membrane is essential for ADMFC operation. The second scenario is used to analyse requirements on water transport through the membrane for different operation conditions. These requirements are influenced by current density, evaporation rate, methanol cross-over and electro-osmotic drag of water. Simulations indicate that water supply is mainly challenging for high current densities and demands on high water diffusion are intensified by water drag. Thus, current density might be limited by water transport through membrane. The presented results help to identify important effects and processes in ADMFCs with a polymer electrolyte membrane and to understand these processes. Furthermore, the requirements identified by modelling show the importance of considering water transport through membrane besides conductivity and methanol cross-over especially for designing new membrane materials. © 2014 Elsevier B.V. All rights reserved.

@article{arlt_operando_2014,
	title = {In operando monitoring of the state of charge and species distribution in zinc air batteries using {X}-ray tomography and model-based simulations},
	volume = {16},
	copyright = {All rights reserved},
	issn = {14639076},
	doi = {10.1039/c4cp02878c},
	abstract = {A novel combination of in operando X-ray tomography and model-based analysis of zinc air batteries is introduced. Using this approach the correlation between the three-dimensional morphological properties of the electrode - on the one hand - and the electrochemical properties of the battery - on the other hand is revealed. In detail, chemical dissolution of zinc particles and the electrode volume were investigated non-destructively during battery operation by X-ray tomography (applying a spatial resolution of 9 μm), while simulation yielded cell potentials of each electrode and allows for the prediction of long-term operation behavior. Furthermore, the analysis of individual zinc particles revealed an electrochemical dissolution process that can be explained using an adapted shrinking-core model.},
	number = {40},
	journal = {Physical Chemistry Chemical Physics},
	author = {Arlt, Tobias and Schröder, Daniel and Krewer, Ulrike and Manke, Ingo},
	year = {2014},
	pmid = {25220061},
	pages = {22273--22280},
}

A novel combination of in operando X-ray tomography and model-based analysis of zinc air batteries is introduced. Using this approach the correlation between the three-dimensional morphological properties of the electrode - on the one hand - and the electrochemical properties of the battery - on the other hand is revealed. In detail, chemical dissolution of zinc particles and the electrode volume were investigated non-destructively during battery operation by X-ray tomography (applying a spatial resolution of 9 μm), while simulation yielded cell potentials of each electrode and allows for the prediction of long-term operation behavior. Furthermore, the analysis of individual zinc particles revealed an electrochemical dissolution process that can be explained using an adapted shrinking-core model.

@article{krewer_scenario-based_2014,
	title = {Scenario-based analysis of potential and constraints of alkaline electrochemical cells},
	volume = {33},
	copyright = {All rights reserved},
	issn = {15707946},
	doi = {10.1016/B978-0-444-63455-9.50041-6},
	abstract = {Alkaline electrochemical cells such as alkaline direct methanol fuel cells and secondary zinc air batteries are attractive low cost and high energy density alternatives to the presently favoured polymer electrolyte membrane fuel cell and Li ion battery. They are presently under development, and materials, geometry and operating conditions which allow high performance have not yet been determined. To assist the development of these exploratory cells, a model-based analysis methodology has been developed and applied. Scenario-based modeling with a reference model of minimum size and more complex variants is presented, and it is shown how feasible transport mechanisms, operating ranges and material properties are identified for these cells. In conclusion, the presented approach is flexibly applicable to various electrochemical and other systems and aids already in the first steps of process development. © 2014 Elsevier B.V.},
	journal = {Computer Aided Chemical Engineering},
	author = {Krewer, Ulrike and Schröder, Daniel and Weinzierl, Christine},
	year = {2014},
	keywords = {Alkaline fuel cell, Feasibility range, Modeling, Water transport, Zinc air battery},
	pages = {1237--1242},
}

Alkaline electrochemical cells such as alkaline direct methanol fuel cells and secondary zinc air batteries are attractive low cost and high energy density alternatives to the presently favoured polymer electrolyte membrane fuel cell and Li ion battery. They are presently under development, and materials, geometry and operating conditions which allow high performance have not yet been determined. To assist the development of these exploratory cells, a model-based analysis methodology has been developed and applied. Scenario-based modeling with a reference model of minimum size and more complex variants is presented, and it is shown how feasible transport mechanisms, operating ranges and material properties are identified for these cells. In conclusion, the presented approach is flexibly applicable to various electrochemical and other systems and aids already in the first steps of process development. © 2014 Elsevier B.V.

@article{mao_total_2013,
	title = {Total harmonic distortion analysis of oxygen reduction reaction in proton exchange membrane fuel cells},
	volume = {103},
	copyright = {All rights reserved},
	issn = {00134686},
	doi = {10.1016/j.electacta.2013.03.194},
	abstract = {The nonlinear frequency response behavior of a proton exchange membrane fuel cell (PEMFC) with different O2stoichiometry is characterized and analyzed by total harmonic distortion (THD) spectroscopy. Damjanovic oxygen reduction reaction (ORR) mechanisms with either oxygen electrochemisorption or oxygen chemisorption are comparatively studied in the simulation through THD spectroscopy and commonly used methods that include steady state current-voltage (I-V) curve and electrochemical impedance spectroscopy (EIS). Comparison results show that only THD spectroscopy is able to make a fine distinction for the ORR mechanisms in certain kinetically controlled frequency ranges. The Damjanovic ORR mechanism with oxygen chemisorption is recognized as a better option for the ORR process in the PEMFC due to the reproducible experimental THD spectra. The observed nonlinear response in the frequency range from 2.5 Hz to 15.8 Hz is also recognized as the fingerprint of the ORR process. © 2013 Published by Elsevier Ltd. All rights reserved.},
	journal = {Electrochimica Acta},
	author = {Mao, Qing and Krewer, Ulrike},
	year = {2013},
	keywords = {Nonlinear frequency response behavior, Oxygen reduction reaction (ORR) mechanism, Total harmonic distortion (THD) spectroscopy},
	pages = {188--198},
}

The nonlinear frequency response behavior of a proton exchange membrane fuel cell (PEMFC) with different O2stoichiometry is characterized and analyzed by total harmonic distortion (THD) spectroscopy. Damjanovic oxygen reduction reaction (ORR) mechanisms with either oxygen electrochemisorption or oxygen chemisorption are comparatively studied in the simulation through THD spectroscopy and commonly used methods that include steady state current-voltage (I-V) curve and electrochemical impedance spectroscopy (EIS). Comparison results show that only THD spectroscopy is able to make a fine distinction for the ORR mechanisms in certain kinetically controlled frequency ranges. The Damjanovic ORR mechanism with oxygen chemisorption is recognized as a better option for the ORR process in the PEMFC due to the reproducible experimental THD spectra. The observed nonlinear response in the frequency range from 2.5 Hz to 15.8 Hz is also recognized as the fingerprint of the ORR process. © 2013 Published by Elsevier Ltd. All rights reserved.

@book{fuhrmann_energy_2013,
	title = {Energy {Storage} {Based} on {Electrochemical} {Conversion} of {Ammonia}},
	copyright = {All rights reserved},
	isbn = {978-3-527-33239-7},
	url = {http://doi.wiley.com/10.1002/9783527673872.ch33},
	abstract = {© 2013 Wiley-VCH Verlag GmbH \& Co. KGaA. All rights reserved. In order to compensate for the volatility of the feed-in of electricity due to the increasing share of renewable energy sources in the electrical grid, the capacity and duration of energy storage need to be increased by orders of magnitude. Among the different options, storage in the form of chemical energy has the advantage of high density and capacity. In this context, along with hydrogen and hydrocarbons, ammonia is attracting increasing interest as a possible energy vector. Its thermodynamic properties are close to those of propane. In the liquid state under close to environmental conditions, it has a higher energy density than hydrogen, and it is usable as a fuel in combustion engines and gas turbines. Currently, nearly all ammonia is produced by the Haber-Bosch-process optimized for continuous mass production; however, optimization for dynamic production seems to be not out of reach. At the laboratory scale, different potentially highly flexible electrochemical routes for ammonia synthesis and conversion to electricity are currently under investigation. This chapter reviews different options for ammonia synthesis and energy recovery under the premise of its use as a storage medium in a renewable energy system.},
	author = {Fuhrmann, Jürgen and Hülsebrock, Marlene and Krewer, Ulrike},
	year = {2013},
	doi = {10.1002/9783527673872.ch33},
	keywords = {ammonia, electrochemical, energy storage},
}

© 2013 Wiley-VCH Verlag GmbH & Co. KGaA. All rights reserved. In order to compensate for the volatility of the feed-in of electricity due to the increasing share of renewable energy sources in the electrical grid, the capacity and duration of energy storage need to be increased by orders of magnitude. Among the different options, storage in the form of chemical energy has the advantage of high density and capacity. In this context, along with hydrogen and hydrocarbons, ammonia is attracting increasing interest as a possible energy vector. Its thermodynamic properties are close to those of propane. In the liquid state under close to environmental conditions, it has a higher energy density than hydrogen, and it is usable as a fuel in combustion engines and gas turbines. Currently, nearly all ammonia is produced by the Haber-Bosch-process optimized for continuous mass production; however, optimization for dynamic production seems to be not out of reach. At the laboratory scale, different potentially highly flexible electrochemical routes for ammonia synthesis and conversion to electricity are currently under investigation. This chapter reviews different options for ammonia synthesis and energy recovery under the premise of its use as a storage medium in a renewable energy system.

@article{mao_sensing_2012,
	title = {Sensing methanol concentration in direct methanol fuel cell with total harmonic distortion: {Theory} and application},
	volume = {68},
	copyright = {All rights reserved},
	issn = {00134686},
	shorttitle = {Sensing methanol concentration in direct methanol fuel cell with total harmonic distortion},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S0013468612002058},
	doi = {10.1016/j.electacta.2012.02.018},
	language = {en},
	urldate = {2019-06-27},
	journal = {Electrochimica Acta},
	author = {Mao, Qing and Krewer, Ulrike},
	month = apr,
	year = {2012},
	pages = {60--68},
}

@inproceedings{behrendt_model_2012,
	title = {Model predictive control of a hybrid fuel cell \& battery power system},
	volume = {8},
	copyright = {All rights reserved},
	isbn = {978-3-902823-05-2},
	doi = {10.3182/20120710-4-SG-2026.00184},
	abstract = {This paper considers optimal operation of an hybrid powered energy system. The two power sources include a direct methanol fuel cell and a lithium-ion battery. A portable system represented by characteristic dynamic load profiles is considered as the consumer. A PI and a nonlinear model predictive control algorithm have been investigated and compared in terms of efficiency and robustness of operation. © 2012 IFAC.},
	booktitle = {{IFAC} {Proceedings} {Volumes} ({IFAC}-{PapersOnline})},
	author = {Behrendt, Martin and Bajcinca, Naim and Zenith, Federico and Krewer, Ulrike},
	year = {2012},
	keywords = {Battery, DMFC, Fuel cell, Nonlinear model predictive control, Optimal control, Portable system},
	pages = {131--136},
}

This paper considers optimal operation of an hybrid powered energy system. The two power sources include a direct methanol fuel cell and a lithium-ion battery. A portable system represented by characteristic dynamic load profiles is considered as the consumer. A PI and a nonlinear model predictive control algorithm have been investigated and compared in terms of efficiency and robustness of operation. © 2012 IFAC.

@article{zenith_effects_2012,
	title = {Effects of process integration in an active direct methanol fuel-cell system},
	volume = {59},
	copyright = {All rights reserved},
	issn = {02552701},
	doi = {10.1016/j.cep.2012.04.007},
	abstract = {This article investigates process integration in a direct methanol fuel-cell system from the points of view of controllability, efficiency, and safety. The two cooling and separation lines of anodic and cathodic effluent from the cell stack of a reference system are integrated into a single one. The potential for process integration is measured quantitatively, determining how much the heat exchangers need to be oversized in the reference system, and qualitatively, considering the expected benefits of a more integrated system. The control layout of the reference system is redesigned for the integrated system, without significant loss in dynamic and steady-state performance. A significant disadvantage of the integrated layout is the increased loss of unreacted methanol from its exhaust, which reduces efficiency and has safety implications. The integrated system is found most appropriate for small, portable systems for which small size and high energy density are particularly important. © 2012 Elsevier B.V.},
	journal = {Chemical Engineering and Processing: Process Intensification},
	author = {Zenith, Federico and Na, Youngseung and Krewer, Ulrike},
	year = {2012},
	keywords = {Control, Direct methanol fuel cell, Dynamic simulation, Process integration},
	pages = {43--51},
}

This article investigates process integration in a direct methanol fuel-cell system from the points of view of controllability, efficiency, and safety. The two cooling and separation lines of anodic and cathodic effluent from the cell stack of a reference system are integrated into a single one. The potential for process integration is measured quantitatively, determining how much the heat exchangers need to be oversized in the reference system, and qualitatively, considering the expected benefits of a more integrated system. The control layout of the reference system is redesigned for the integrated system, without significant loss in dynamic and steady-state performance. A significant disadvantage of the integrated layout is the increased loss of unreacted methanol from its exhaust, which reduces efficiency and has safety implications. The integrated system is found most appropriate for small, portable systems for which small size and high energy density are particularly important. © 2012 Elsevier B.V.

@article{yu_direct_2012,
	title = {Direct oxidation alkaline fuelcells: from materials to systems},
	volume = {5},
	copyright = {All rights reserved},
	issn = {1754-5692},
	url = {http://xlink.rsc.org/?DOI=C2EE02552C},
	doi = {10.1039/C2EE02552C},
	abstract = {Low cost fuel cells: challenges and future development of direct oxidation alkaline fuel cells.},
	number = {2},
	journal = {Energy Environ. Sci.},
	author = {Yu, Eileen Hao and Wang, Xu and Krewer, Ulrike and Li, Lei and Scott, Keith},
	year = {2012},
	pages = {5668--5680},
}

Low cost fuel cells: challenges and future development of direct oxidation alkaline fuel cells.

@article{stenger_feasibility_2012,
	title = {Feasibility {Study} of a {Fossile} {Fueled} {Zero} {Emission} {Vehicle}},
	volume = {1},
	copyright = {All rights reserved},
	issn = {2167-4205},
	url = {http://papers.sae.org/2012-01-1650/},
	doi = {10.4271/2012-01-1650},
	abstract = {This study investigates the technical feasibility of onboard carbon capture in vehicles. In fact there are two different main concepts of hybrid electric vehicles with batteries and range extenders proposed. The first concept uses an Internal Combustion Engine as range extender. Carbon dioxide is separated from the flue gas of this Internal Combustion Engine by chemical or physical absorption. In the second concept a solid oxide fuel cell (SOFC) is used as a range extender. The CO remaining in the anode exhaust gas is not combusted as usual by mixing anode and cathode exhaust gases but shifted with water vapor, sufficient available in the anode exhaust gas flow, to H2 and CO2. The H2 is separated by a membrane permeable only for H2 and recycled by the methane flow to the SOFC stack. Carbon dioxide can then be separated by simply condensing the water vapor of the anode exhaust gas of the SOFC. Carbon dioxide can either remain onboard chemically bonded e.g. as carbonate with the absorption media or stored in a pressure vessel after desorption or condensation of the water vapor. As one mole methane produces one mole CO2, the CO2 can be stored in one chamber of a double chamber tank. The tank is e.g. divided into two chambers with variable volume by a non-permeable but flexible membrane; on the other side of this membrane methane is stored. At the gasoline station the empty methane chamber is filled with new methane and the CO2 is discharged simultaneously providing also simple fueling and CO2 removal methods. Carbonate can also be disposed at the gasoline station and calcinated in centralized plants, i.e. CO2 can be separated and CaO reused. Furthermore all concepts are compared in fuel efficiency and general feasibility. The SOFC concept seems to be the most attractive one, because it shows the highest efficiency, uses the simplest CO2 capture concept and releases the captured CO2 in gaseous state, providing the simplest CO2 discharging method.},
	number = {2},
	journal = {SAE International Journal of Alternative Powertrains},
	author = {Stenger, Sebastian and Köhler, Steffi and Nasch, Anna-Theresia and Leithner, Reinhard and Scholl, Stephan and Krewer, Ulrike and Eilts, Peter},
	year = {2012},
	pages = {2012--01--1650},
}

This study investigates the technical feasibility of onboard carbon capture in vehicles. In fact there are two different main concepts of hybrid electric vehicles with batteries and range extenders proposed. The first concept uses an Internal Combustion Engine as range extender. Carbon dioxide is separated from the flue gas of this Internal Combustion Engine by chemical or physical absorption. In the second concept a solid oxide fuel cell (SOFC) is used as a range extender. The CO remaining in the anode exhaust gas is not combusted as usual by mixing anode and cathode exhaust gases but shifted with water vapor, sufficient available in the anode exhaust gas flow, to H2 and CO2. The H2 is separated by a membrane permeable only for H2 and recycled by the methane flow to the SOFC stack. Carbon dioxide can then be separated by simply condensing the water vapor of the anode exhaust gas of the SOFC. Carbon dioxide can either remain onboard chemically bonded e.g. as carbonate with the absorption media or stored in a pressure vessel after desorption or condensation of the water vapor. As one mole methane produces one mole CO2, the CO2 can be stored in one chamber of a double chamber tank. The tank is e.g. divided into two chambers with variable volume by a non-permeable but flexible membrane; on the other side of this membrane methane is stored. At the gasoline station the empty methane chamber is filled with new methane and the CO2 is discharged simultaneously providing also simple fueling and CO2 removal methods. Carbonate can also be disposed at the gasoline station and calcinated in centralized plants, i.e. CO2 can be separated and CaO reused. Furthermore all concepts are compared in fuel efficiency and general feasibility. The SOFC concept seems to be the most attractive one, because it shows the highest efficiency, uses the simplest CO2 capture concept and releases the captured CO2 in gaseous state, providing the simplest CO2 discharging method.

@article{zenith_model-based_2012,
	title = {Model-based analysis of micro-separators for portable direct methanol fuel-cell systems},
	volume = {38},
	copyright = {All rights reserved},
	issn = {00981354},
	doi = {10.1016/j.compchemeng.2011.11.005},
	abstract = {The applicability of capillary separation to direct methanol fuel-cell systems is studied in this article from two complementary perspectives: a three-dimensional simulation with computational fluid dynamics of a gas-liquid separator, whose function is based on capillary forces rather than gravity, and a zero-dimensional model, which is integrated in the process model of a direct methanol fuel-cell system. The three-dimensional analysis indicates that an appropriate choice of construction and operation parameters allows to achieve almost perfect gas-liquid separation, and that operation is not significantly influenced by orientation. The system-wide analysis indicates that the inclusion of such a capillary separator stabilises the system, allowing the use of simpler control strategies and removing the necessity of sensors difficult to implement. © 2011 Elsevier Ltd.},
	journal = {Computers and Chemical Engineering},
	author = {Zenith, Federico and Kraus, Maik and Krewer, Ulrike},
	year = {2012},
	keywords = {Capillary, Computational fluid dynamics, Control, Fuel cell, Orientation},
	pages = {64--73},
}

The applicability of capillary separation to direct methanol fuel-cell systems is studied in this article from two complementary perspectives: a three-dimensional simulation with computational fluid dynamics of a gas-liquid separator, whose function is based on capillary forces rather than gravity, and a zero-dimensional model, which is integrated in the process model of a direct methanol fuel-cell system. The three-dimensional analysis indicates that an appropriate choice of construction and operation parameters allows to achieve almost perfect gas-liquid separation, and that operation is not significantly influenced by orientation. The system-wide analysis indicates that the inclusion of such a capillary separator stabilises the system, allowing the use of simpler control strategies and removing the necessity of sensors difficult to implement. © 2011 Elsevier Ltd.

@article{kamat_adsorptionshysterese_2012,
	title = {Adsorptionshysterese von {Phosphorsäure} in {Polybenzimidazol}- {Hochtemperatur}-{Polymerelektrolytmembran}-{Brennstoffzellen}},
	volume = {84},
	copyright = {All rights reserved},
	issn = {0009286X},
	doi = {10.1002/cite.201100249},
	number = {12},
	journal = {Chemie-Ingenieur-Technik},
	author = {Kamat, Ashish and Klein, Olaf and Herrmann, Mirko and Krewer, Ulrike and Scholl, Stephan},
	year = {2012},
	keywords = {Adsorption, Hysteresis, PBI high temperature PEM fuel cell, Phosphoric acid, Surface coverage, Tafel equation},
	pages = {2198--2203},
}

@inproceedings{kamat_experimental_2011,
	title = {Experimental investigations into phosphoric acid adsorption on platinum catalysts in a high temperature {PEM} {Fuel} cell},
	volume = {11},
	copyright = {All rights reserved},
	isbn = {1615-6846},
	doi = {10.1002/fuce.201000102},
	abstract = {Dynamic testing of a phosphoric acid-based high temperature PEM fuel cell shows a peculiar phenomenon. A certain current loss is observed after temperature cycling at constant voltage. This loss is incidentally recovered by applying a cell voltage spike to open circuit voltage. Experimental investigations into temperature, cell voltage, and ageing effects show that this phenomenon might occur due to the orientation of the adsorbed phosphate species on the platinum catalyst surface. Along with some supporting literature and experimental results, a hypothesis is presented in order to explain this occurrence. Phosphoric acid adsorption hysteresis on platinum catalyst due to temperature cycling could cause the temporary cell current loss. Electrode potential-dependent molecule symmetry of adsorbed phosphate ions could bring about the cell current recovery.},
	booktitle = {Fuel {Cells}},
	author = {Kamat, A. and Herrmann, M. and Ternes, D. and Klein, O. and Krewer, U. and Scholl, S.},
	year = {2011},
	keywords = {Adsorbate Orientation, Fuel Cells, HT PEM, Hysteresis, Phosphoric Acid Adsorption, Platinum Catalysts, Temperature Cycling},
	pages = {511--517},
}

Dynamic testing of a phosphoric acid-based high temperature PEM fuel cell shows a peculiar phenomenon. A certain current loss is observed after temperature cycling at constant voltage. This loss is incidentally recovered by applying a cell voltage spike to open circuit voltage. Experimental investigations into temperature, cell voltage, and ageing effects show that this phenomenon might occur due to the orientation of the adsorbed phosphate species on the platinum catalyst surface. Along with some supporting literature and experimental results, a hypothesis is presented in order to explain this occurrence. Phosphoric acid adsorption hysteresis on platinum catalyst due to temperature cycling could cause the temporary cell current loss. Electrode potential-dependent molecule symmetry of adsorbed phosphate ions could bring about the cell current recovery.

@book{krewer_electrochemical_2011,
	title = {Electrochemical oxidation of carbon-containing fuels and their dynamics in low-temperature fuel cells},
	volume = {12},
	copyright = {All rights reserved},
	isbn = {1439-7641},
	abstract = {Fuel cells can convert the energy that is chemically stored in a compound into electrical energy with high efficiency. Hydrogen could be the first choice for chemical energy storage, but its utilization is limited due to storage and transport difficulties. Carbon-containing fuels store chemical energy with significantly higher energy density, which makes them excellent energy carriers. The electro-oxidation of carbon-containing fuels without prior reforming is a more challenging and complex process than anodic hydrogen oxidation. The current understanding of the direct electro-oxidation of carbon-containing fuels in low-temperature fuel cells is reviewed. Furthermore, this review covers various aspects of electro-oxidation for carbon-containing fuels in non-steady-state reaction conditions. Such dynamic investigations open possibilities to elucidate detailed reaction kinetics, to sense fuel concentration, or to diagnose the fuel-cell state during operation. Motivated by the challenge to decrease the consumption of fossil fuel, the production routes of the fuels from renewable resources also are reviewed.},
	number = {14},
	author = {Krewer, Ulrike and Vidakovic-Koch, Tanja and Rihko-Struckmann, Liisa},
	year = {2011},
	doi = {10.1002/cphc.201100095},
	pmid = {21755584},
	keywords = {dynamic operations, electro-oxidation, fuel cells, kinetics, reaction mechanisms},
}

Fuel cells can convert the energy that is chemically stored in a compound into electrical energy with high efficiency. Hydrogen could be the first choice for chemical energy storage, but its utilization is limited due to storage and transport difficulties. Carbon-containing fuels store chemical energy with significantly higher energy density, which makes them excellent energy carriers. The electro-oxidation of carbon-containing fuels without prior reforming is a more challenging and complex process than anodic hydrogen oxidation. The current understanding of the direct electro-oxidation of carbon-containing fuels in low-temperature fuel cells is reviewed. Furthermore, this review covers various aspects of electro-oxidation for carbon-containing fuels in non-steady-state reaction conditions. Such dynamic investigations open possibilities to elucidate detailed reaction kinetics, to sense fuel concentration, or to diagnose the fuel-cell state during operation. Motivated by the challenge to decrease the consumption of fossil fuel, the production routes of the fuels from renewable resources also are reviewed.

@book{krewer_portable_2011,
	title = {Portable {Energiesysteme}: {Von} elektrochemischer {Wandlung} bis {Energy} {Harvesting}},
	volume = {83},
	copyright = {All rights reserved},
	abstract = {Portable energy systems supply electrical power at any location. The most wide-spread portable energy systems are electrochemical energy storage systems, especially batteries. Batteries have a limited operating range and limited amount of stored energy; suitable replacements are energy converters like fuel cells, microturbines or energy harvesting technologies. This review gives an overview on all portable energy technologies from the point of view of process engineering, compares the technologies and discusses recent and future trends. © 2011 WILEY-VCH Verlag GmbH \& Co. KGaA, Weinheim.},
	number = {11},
	author = {Krewer, Ulrike},
	year = {2011},
	doi = {10.1002/cite.201100084},
	keywords = {Batteries, Energy conversion, Energy storage, Fuel cells, Microsystems engineering},
}

Portable energy systems supply electrical power at any location. The most wide-spread portable energy systems are electrochemical energy storage systems, especially batteries. Batteries have a limited operating range and limited amount of stored energy; suitable replacements are energy converters like fuel cells, microturbines or energy harvesting technologies. This review gives an overview on all portable energy technologies from the point of view of process engineering, compares the technologies and discusses recent and future trends. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

@article{zenith_simple_2011,
	title = {Simple and reliable model for estimation of methanol cross-over in direct methanol fuel cells and its application on methanol-concentration control},
	volume = {4},
	copyright = {All rights reserved},
	issn = {17545692},
	doi = {10.1039/c0ee00415d},
	abstract = {A simplified model of mass-transport phenomena on the anodic side of direct methanol fuel cells (DMFCs) is presented, with the objective of estimating the cross-over flux in order to enable feedforward (sensorless) control of anodic concentration in DMFC systems. The effect of parameter uncertainty on the tracking error of the control system is analysed and several models for temperature dependence are proposed. Experimental data on methanol cross-over was gathered in a DMFC system, and the models were discriminated by means of nonlinear regression. The regression results and an initial test run indicate that feedforward control of anodic methanol concentration in DMFC systems is feasible. © 2011 The Royal Society of Chemistry.},
	number = {2},
	journal = {Energy and Environmental Science},
	author = {Zenith, Federico and Krewer, Ulrike},
	year = {2011},
	pages = {519--527},
}

A simplified model of mass-transport phenomena on the anodic side of direct methanol fuel cells (DMFCs) is presented, with the objective of estimating the cross-over flux in order to enable feedforward (sensorless) control of anodic concentration in DMFC systems. The effect of parameter uncertainty on the tracking error of the control system is analysed and several models for temperature dependence are proposed. Experimental data on methanol cross-over was gathered in a DMFC system, and the models were discriminated by means of nonlinear regression. The regression results and an initial test run indicate that feedforward control of anodic methanol concentration in DMFC systems is feasible. © 2011 The Royal Society of Chemistry.

@inproceedings{krewer_model-based_2011,
	title = {Model-based {Analysis} of the {Environmental} {Operating} {Range} of {Direct} {Methanol} {Fuel} {Cell} {Systems}},
	copyright = {All rights reserved},
	booktitle = {Proceedings of the {European} {Fuel} {Cell} {Forum} 2011},
	author = {Krewer, Ulrike and Zenith, Federico and Weinzierl, Christine},
	year = {2011},
	pages = {1--7},
}

@article{yu_principles_2010,
	title = {Principles and {Materials} {Aspects} of {Direct} {Alkaline} {Alcohol} {Fuel} {Cells}},
	volume = {3},
	copyright = {All rights reserved},
	issn = {1996-1073},
	url = {http://www.mdpi.com/1996-1073/3/8/1499},
	doi = {10.3390/en3081499},
	language = {en},
	number = {8},
	urldate = {2019-06-03},
	journal = {Energies},
	author = {Yu, Eileen Hao and Krewer, Ulrike and Scott, Keith},
	month = aug,
	year = {2010},
	pages = {1499--1528},
}

@article{zenith_modelling_2010,
	title = {Modelling, dynamics and control of a portable {DMFC} system},
	volume = {20},
	copyright = {All rights reserved},
	issn = {09591524},
	doi = {10.1016/j.jprocont.2010.02.014},
	abstract = {A dynamic model for a direct methanol fuel cell and its ancillary units is presented, in which all ancillary units perform only one operation each. The system's losses and main dynamics (cathodic oxygen fraction, anodic methanol concentration, stack temperature, system water holdup) are analysed for stability and time constants. The system is found to be stable in all of its dynamics except for that of water holdup. The influence of external conditions, such as temperature and humidity, on system feasibility is analysed; the capability of system autonomous operation depends essentially on environmental conditions and on the chosen air excess ratio. Decoupled single-input, single-output controllers, some of which employing feedback, are applied to maintain the system at a certain set point. System simulations are performed, confirming the performance of the proposed controllers, their ability to stabilise the water holdup, and the absence of interaction-induced oscillations; the system can be started up in about ten minutes with the presented parameters. © 2010 Elsevier Ltd. All rights reserved.},
	number = {5},
	journal = {Journal of Process Control},
	author = {Zenith, Federico and Krewer, Ulrike},
	year = {2010},
	keywords = {Autonomy, Control, Dynamics, Fuel cells, Methanol, System},
	pages = {630--642},
}

A dynamic model for a direct methanol fuel cell and its ancillary units is presented, in which all ancillary units perform only one operation each. The system's losses and main dynamics (cathodic oxygen fraction, anodic methanol concentration, stack temperature, system water holdup) are analysed for stability and time constants. The system is found to be stable in all of its dynamics except for that of water holdup. The influence of external conditions, such as temperature and humidity, on system feasibility is analysed; the capability of system autonomous operation depends essentially on environmental conditions and on the chosen air excess ratio. Decoupled single-input, single-output controllers, some of which employing feedback, are applied to maintain the system at a certain set point. System simulations are performed, confirming the performance of the proposed controllers, their ability to stabilise the water holdup, and the absence of interaction-induced oscillations; the system can be started up in about ten minutes with the presented parameters. © 2010 Elsevier Ltd. All rights reserved.

@article{mao_total_2010,
	title = {Total harmonic distortion analysis for direct methanol fuel cell anode},
	volume = {12},
	copyright = {All rights reserved},
	issn = {13882481},
	doi = {10.1016/j.elecom.2010.08.022},
	abstract = {In this study, total harmonic distortion (THD) analysis is put forward to illustrate nonlinear behavior of direct methanol fuel cell (DMFC) anode. THD simulations by means of different methanol oxidation kinetics as well as its experimental validation are both carried out. It is shown that the THD model adopting a three-step methanol oxidation mechanism with Kauranen-Frumkin/Temkin kinetics can be used to illustrate the THD variation for DMFC anode qualitatively. The experimental THD response at the frequency range from 0.063 Hz to 0.4 Hz is identified as the reflection of the nonlinearity variation of those kinetic steps involving intermediates in the methanol oxidation. In such a frequency domain, THD value decrease monotonously with decreasing methanol concentration, which notices its accessibility on methanol concentration detection. © 2010 Elsevier B.V. All rights reserved.},
	number = {11},
	journal = {Electrochemistry Communications},
	author = {Mao, Qing and Krewer, Ulrike and Hanke-Rauschenbach, Richard},
	year = {2010},
	keywords = {DMFC, Methanol concentration, Nonlinear behavior, Total harmonic distortion (THD) analysis},
	pages = {1517--1519},
}

In this study, total harmonic distortion (THD) analysis is put forward to illustrate nonlinear behavior of direct methanol fuel cell (DMFC) anode. THD simulations by means of different methanol oxidation kinetics as well as its experimental validation are both carried out. It is shown that the THD model adopting a three-step methanol oxidation mechanism with Kauranen-Frumkin/Temkin kinetics can be used to illustrate the THD variation for DMFC anode qualitatively. The experimental THD response at the frequency range from 0.063 Hz to 0.4 Hz is identified as the reflection of the nonlinearity variation of those kinetic steps involving intermediates in the methanol oxidation. In such a frequency domain, THD value decrease monotonously with decreasing methanol concentration, which notices its accessibility on methanol concentration detection. © 2010 Elsevier B.V. All rights reserved.

@article{zenith_model-based_2010,
	title = {Model-based analysis of the feasibility envelope for autonomous operation of a portable direct methanol fuel-cell system},
	volume = {65},
	copyright = {All rights reserved},
	issn = {00092509},
	doi = {10.1016/j.ces.2010.03.055},
	abstract = {Portable power systems based on direct methanol fuel cells (DMFC) have to provide power in various environmental conditions: it is advantageous for such a power-supply system to be autonomous, i.e. able to operate without water refills for the methanol solution. It is shown that system autonomy depends mainly on environmental humidity, condenser temperature and air excess ratio: this result is valid in general for any DMFC, as cell parameters have only a marginal role. The environmental conditions in which a portable DMFC system may be autonomous are considered, delineating a feasibility envelope. Two methods are proposed to extend this envelope: operating with a diluted methanol reservoir, which improves the autonomy of the system only marginally and at the cost of a large loss in energy density, and system pressurisation, which delivers a more significant improvement in autonomy properties, but at the cost of system efficiency and simplicity. ?? 2010 Elsevier Ltd. All rights reserved.},
	number = {15},
	journal = {Chemical Engineering Science},
	author = {Zenith, Federico and Weinzierl, Christine and Krewer, Ulrike},
	year = {2010},
	keywords = {Autonomy, Chemical processes, Evaporation, Fuel cells, Mathematical modelling, Numerical analysis, Portability},
	pages = {4411--4419},
}

Portable power systems based on direct methanol fuel cells (DMFC) have to provide power in various environmental conditions: it is advantageous for such a power-supply system to be autonomous, i.e. able to operate without water refills for the methanol solution. It is shown that system autonomy depends mainly on environmental humidity, condenser temperature and air excess ratio: this result is valid in general for any DMFC, as cell parameters have only a marginal role. The environmental conditions in which a portable DMFC system may be autonomous are considered, delineating a feasibility envelope. Two methods are proposed to extend this envelope: operating with a diluted methanol reservoir, which improves the autonomy of the system only marginally and at the cost of a large loss in energy density, and system pressurisation, which delivers a more significant improvement in autonomy properties, but at the cost of system efficiency and simplicity. ?? 2010 Elsevier Ltd. All rights reserved.

@article{arisetty_coupling_2010,
	title = {Coupling of {Kinetic} and {Mass} {Transfer} {Processes} in {Direct} {Methanol} {Fuel} {Cells}},
	volume = {157},
	copyright = {All rights reserved},
	issn = {00134651},
	url = {http://jes.ecsdl.org/cgi/doi/10.1149/1.3478142},
	doi = {10.1149/1.3478142},
	abstract = {A model coupling momentum transport with reaction kinetics within the five-layer membrane electrode assembly has been developed for direct methanol fuel cells (DMFCs). The model accounts for the essential intermediate reaction steps on both anode and cathode catalyst layers, as well as the two-phase phenomena in the anode and cathode gas diffusion layers. The kinetics of the methanol reaction on the cathode catalyst layer that separately account for both chemical and electrochemical pathways are investigated. The model predictions agree with the DMFC experimental data. Simulation results indicate that the transport of methanol is essential in determining both the anode and cathode kinetics. Anode kinetics are not significantly improved for anode concentrations above 2 M. It is also revealed that the transport of methanol to the anode catalyst layer is significantly enhanced by the convection of CO2 bubbles toward the flow field. The influence of methanol crossover on the cathode potential is quantified by changing the anode feed from methanol to hydrogen. The cathode potential is seen to deteriorate at higher methanol feed concentrations mainly due to the depletion of oxygen by the crossed over methanol on the cathode catalyst. This model should prove useful in optimizing the methanol feed concentration in DMFCs.},
	number = {10},
	journal = {Journal of The Electrochemical Society},
	author = {Arisetty, Srikanth and Krewer, Ulrike and Advani, Suresh G. and Prasad, Ajay K.},
	year = {2010},
	pages = {B1443},
}

A model coupling momentum transport with reaction kinetics within the five-layer membrane electrode assembly has been developed for direct methanol fuel cells (DMFCs). The model accounts for the essential intermediate reaction steps on both anode and cathode catalyst layers, as well as the two-phase phenomena in the anode and cathode gas diffusion layers. The kinetics of the methanol reaction on the cathode catalyst layer that separately account for both chemical and electrochemical pathways are investigated. The model predictions agree with the DMFC experimental data. Simulation results indicate that the transport of methanol is essential in determining both the anode and cathode kinetics. Anode kinetics are not significantly improved for anode concentrations above 2 M. It is also revealed that the transport of methanol to the anode catalyst layer is significantly enhanced by the convection of CO2 bubbles toward the flow field. The influence of methanol crossover on the cathode potential is quantified by changing the anode feed from methanol to hydrogen. The cathode potential is seen to deteriorate at higher methanol feed concentrations mainly due to the depletion of oxygen by the crossed over methanol on the cathode catalyst. This model should prove useful in optimizing the methanol feed concentration in DMFCs.

@article{krewer_kinetisch_2009,
	title = {Kinetisch und dynamisch},
	volume = {57},
	copyright = {All rights reserved},
	issn = {14399598},
	url = {http://doi.wiley.com/10.1002/nadc.200965649},
	doi = {10.1002/nadc.200965649},
	language = {de},
	number = {7-8},
	urldate = {2019-06-26},
	journal = {Nachrichten aus der Chemie},
	author = {Krewer, U. and {Hanke-Rauschenbach}},
	month = jul,
	year = {2009},
	pages = {753--756},
}

@inproceedings{zenith_dynamics_2009,
	title = {Dynamics and {Control} of a {Portable} {DMFC} {System}},
	copyright = {All rights reserved},
	isbn = {978-0-7918-4881-4},
	url = {http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=1646381},
	doi = {10.1115/FuelCell2009-85115},
	booktitle = {{ASME} 2009 7th {International} {Conference} on {Fuel} {Cell} {Science}, {Engineering} and {Technology}},
	publisher = {ASME},
	author = {Zenith, Federico and Krewer, Ulrike},
	month = jan,
	year = {2009},
	keywords = {Direct methanol fuel cells, Dynamics (Mechanics)},
	pages = {351--360},
}

@article{krewer_low_2009,
	title = {Low and high temperature storage characteristics of membrane electrode assemblies for direct methanol fuel cells},
	volume = {187},
	copyright = {All rights reserved},
	issn = {03787753},
	doi = {10.1016/j.jpowsour.2008.10.100},
	abstract = {This paper investigates changes in the performance of membrane electrode assemblies (MEAs) of Direct Methanol Fuel Cells (DMFC) that are caused by undergoing storage at -10 °C and 60 °C under different experimental conditions. Storage at 60 °C exhibited negative effects on an MEA's performance only when storing the MEA at a 4 M CH3OH solution. Here, application of a reverse current for 10 s was found to reinstall the original performance. The effect of storage at -10 °C on an MEA's performance strongly depends upon the MEA's properties. MEAs are grouped into three different categories with regard to their suitability for low temperature storage: not affected, temporarily affected, irreversibly affected. The temporarily affected MEAs could be instantly and completely reactivated by a reverse current. Changes in the MEA properties that had been caused by being stored at -10 °C were investigated for two MEAs using electrochemical methods, scanning electron microscopy and porosity measurements. The following MEA materials and manufacturing methods had been found to be principally suitable to build MEAs tolerant to storage at -10 °C: the manufacturing methods CCM (catalyst coated on the membrane) and CCS (catalyst coated on the substrate), several hydrocarbon membranes, high Pt and Pt-Ru catalyst loadings. By carefully selecting the proper MEA material, MEAs with tolerance towards low and high storage temperatures can be designed. © 2008 Elsevier B.V. All rights reserved.},
	number = {1},
	journal = {Journal of Power Sources},
	author = {Krewer, Ulrike and Park, Jun Young and Lee, Jin Hwa and Cho, Hyejung and Pak, Chanho and You, Dae Jong and Lee, Yoon Hoi},
	year = {2009},
	keywords = {Deactivation, Freezing, Hydrocarbon membrane, Performance loss prevention, Reactivation, Sub-zero storage},
	pages = {103--111},
}

This paper investigates changes in the performance of membrane electrode assemblies (MEAs) of Direct Methanol Fuel Cells (DMFC) that are caused by undergoing storage at -10 °C and 60 °C under different experimental conditions. Storage at 60 °C exhibited negative effects on an MEA's performance only when storing the MEA at a 4 M CH3OH solution. Here, application of a reverse current for 10 s was found to reinstall the original performance. The effect of storage at -10 °C on an MEA's performance strongly depends upon the MEA's properties. MEAs are grouped into three different categories with regard to their suitability for low temperature storage: not affected, temporarily affected, irreversibly affected. The temporarily affected MEAs could be instantly and completely reactivated by a reverse current. Changes in the MEA properties that had been caused by being stored at -10 °C were investigated for two MEAs using electrochemical methods, scanning electron microscopy and porosity measurements. The following MEA materials and manufacturing methods had been found to be principally suitable to build MEAs tolerant to storage at -10 °C: the manufacturing methods CCM (catalyst coated on the membrane) and CCS (catalyst coated on the substrate), several hydrocarbon membranes, high Pt and Pt-Ru catalyst loadings. By carefully selecting the proper MEA material, MEAs with tolerance towards low and high storage temperatures can be designed. © 2008 Elsevier B.V. All rights reserved.

@article{krewer_basic_2008,
	title = {Basic model for membrane electrode assembly design for direct methanol fuel cells},
	volume = {175},
	copyright = {All rights reserved},
	issn = {03787753},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S0378775307022495},
	doi = {10.1016/j.jpowsour.2007.09.115},
	language = {en},
	number = {2},
	urldate = {2019-06-26},
	journal = {Journal of Power Sources},
	author = {Krewer, Ulrike and Yoon, Hae-Kwon and Kim, Hee-Tak},
	month = jan,
	year = {2008},
	pages = {760--772},
}

@article{ko_non-isothermal_2008,
	title = {Non-isothermal dynamic modelling and optimization of a direct methanol fuel cell},
	volume = {180},
	copyright = {All rights reserved},
	issn = {03787753},
	doi = {10.1016/j.jpowsour.2008.01.083},
	abstract = {A non-isothermal dynamic optimization model of direct methanol fuel cells (DMFCs) is developed to predict their performance with an effective optimum-operating strategy. After investigating the sensitivities of the transient behaviour (the outlet temperature, crossovers of methanol and water, and cell voltage) to operating conditions (the inlet flow rates into anode and cathode compartments, and feed concentration) through dynamic simulations, we find that anode feed concentration has a significantly larger impact on methanol crossover, temperature, and cell voltage than the anode and cathode flow rates. Also, optimum transient conditions to satisfy the desired fuel efficiency are obtained by dynamic optimization. In the developed model, the significant influence of temperature on DMFC behaviour is described in detail with successful estimation of its model parameters. ?? 2008 Elsevier B.V. All rights reserved.},
	number = {1},
	journal = {Journal of Power Sources},
	author = {Ko, DaeHo and Lee, MinJeong and Jang, Won Hyouk and Krewer, Ulrike},
	year = {2008},
	keywords = {Direct methanol fuel cell, Dynamic simulation and optimization, Non-isothermal model, Optimum operation},
	pages = {71--83},
}

A non-isothermal dynamic optimization model of direct methanol fuel cells (DMFCs) is developed to predict their performance with an effective optimum-operating strategy. After investigating the sensitivities of the transient behaviour (the outlet temperature, crossovers of methanol and water, and cell voltage) to operating conditions (the inlet flow rates into anode and cathode compartments, and feed concentration) through dynamic simulations, we find that anode feed concentration has a significantly larger impact on methanol crossover, temperature, and cell voltage than the anode and cathode flow rates. Also, optimum transient conditions to satisfy the desired fuel efficiency are obtained by dynamic optimization. In the developed model, the significant influence of temperature on DMFC behaviour is described in detail with successful estimation of its model parameters. ?? 2008 Elsevier B.V. All rights reserved.

@inproceedings{krewer_storage_2008,
	title = {Storage of {DMFC} {MEA} at extreme temperatures},
	copyright = {All rights reserved},
	isbn = {0-7918-4318-1},
	doi = {10.1115/FuelCell2008-65018},
	abstract = {This paper investigates the change in performance of DMFC membrane electrode assemblies (MEAs) after storage at -10°C and 60°C under different experimental conditions. It highlights the importance of methanol concentration, an MEA's material properties such as membrane material and catalyst loading, as well as the reactivation procedure. Storage at 60°C and concentrations below IM methanol had no negative effect on MEA performance while storage at 60°C in a 4 M methanol solution could cause a severe performance decrease. Application of a reverse current for 10 s to a MEA which was affected by such storage was found to reinstall original performance. The effect of storage at -10°C on MEA performance strongly depends on MEA properties. MEAs are grouped into three different categories with regard to suitability for low temperature storage: not affected, reversibly affected, and irreversibly affected. The reversibly affected MEAs could be instantly and completely reactivated by reverse current. MEA materials such as various hydrocarbon membranes and high catalyst loadings as well as the manufacturing methods CCM (catalyst coated on the membrane) and CCS (catalyst coated on the substrate) were found to be principally suitable to build MEAs tolerant to storage at -10°C. Copyright ©2008 by ASME.},
	booktitle = {Proceedings of the 6th {International} {Conference} on {Fuel} {Cell} {Science}, {Engineering}, and {Technology}},
	author = {Krewer, U. and Park, J. and Lee, J. and Cho, H.},
	year = {2008},
	keywords = {Deactivation, Freezing, Performance loss prevention, Reactivation, Sub-zero storage},
}

This paper investigates the change in performance of DMFC membrane electrode assemblies (MEAs) after storage at -10°C and 60°C under different experimental conditions. It highlights the importance of methanol concentration, an MEA's material properties such as membrane material and catalyst loading, as well as the reactivation procedure. Storage at 60°C and concentrations below IM methanol had no negative effect on MEA performance while storage at 60°C in a 4 M methanol solution could cause a severe performance decrease. Application of a reverse current for 10 s to a MEA which was affected by such storage was found to reinstall original performance. The effect of storage at -10°C on MEA performance strongly depends on MEA properties. MEAs are grouped into three different categories with regard to suitability for low temperature storage: not affected, reversibly affected, and irreversibly affected. The reversibly affected MEAs could be instantly and completely reactivated by reverse current. MEA materials such as various hydrocarbon membranes and high catalyst loadings as well as the manufacturing methods CCM (catalyst coated on the membrane) and CCS (catalyst coated on the substrate) were found to be principally suitable to build MEAs tolerant to storage at -10°C. Copyright ©2008 by ASME.

@article{schultz_impact_2007,
	title = {Impact of electrode kinetics on the dynamic response of a {DMFC} to change of methanol feed concentration},
	volume = {165},
	copyright = {All rights reserved},
	issn = {03787753},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S0378775306023949},
	doi = {10.1016/j.jpowsour.2006.11.021},
	language = {en},
	number = {1},
	urldate = {2019-06-26},
	journal = {Journal of Power Sources},
	author = {Schultz, Thorsten and Krewer, Ulrike and Sundmacher, Kai},
	month = feb,
	year = {2007},
	pages = {138--151},
}

@article{krewer_understanding_2007,
	title = {Understanding the dynamic behaviour of direct methanol fuel cells: {Response} to step changes in cell current},
	volume = {609},
	copyright = {All rights reserved},
	issn = {15726657},
	shorttitle = {Understanding the dynamic behaviour of direct methanol fuel cells},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S0022072807002914},
	doi = {10.1016/j.jelechem.2007.06.015},
	language = {en},
	number = {2},
	urldate = {2019-06-26},
	journal = {Journal of Electroanalytical Chemistry},
	author = {Krewer, U. and Kamat, A. and Sundmacher, K.},
	month = nov,
	year = {2007},
	pages = {105--119},
}

@article{krewer_hydrodynamic_2007,
	title = {Hydrodynamic characterisation and modelling of anode flow fields of {Direct} {Methanol} {Fuel} {Cells}},
	volume = {126},
	copyright = {All rights reserved},
	issn = {13858947},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S1385894706003743},
	doi = {10.1016/j.cej.2006.09.001},
	language = {en},
	number = {2-3},
	urldate = {2019-06-26},
	journal = {Chemical Engineering Journal},
	author = {Krewer, U. and Pfafferodt, M. and Kamat, A. and Menendez, D. Fernandez and Sundmacher, K.},
	month = feb,
	year = {2007},
	pages = {87--102},
}

@inproceedings{reshetenko_effect_2007,
	title = {The effect of the anode loading and method of {MEA} fabrication on {DMFC} performance},
	volume = {7},
	copyright = {All rights reserved},
	isbn = {1615-6854},
	doi = {10.1002/fuce.200600030},
	abstract = {The influence of the Pt-Ru anode loading and MEA preparation techniques on direct methanol fuel cell (DMFC) performance is studied. Two different anode catalyst layer preparation techniques are employed. One is the direct coating of anode catalyst ink on a membrane to form a catalyst coated membrane, CCManode, and the other is the coating of the ink on the diffusion layers, which generates a catalyst coated substrate, CCSanode. The power density of a combined CCManode/CCScathode MEA is higher than for a CCSanode/CCScathode MEA. The main difference in the performance is observed in the high current density region, where two-phase flow is present and mass transfer processes govern the performance. The CCManode and CCSanode have different macroscopic structures, while showing the same microscopic morphology. Based on their morphological differences, it is expected that the combination of the CCManode and carbon paper provides the more homogeneous removal of CO2 at high currents. The authors suggest that the application of the CCManode with an optimal anode loading improves anode mass transfer, reduces methanol crossover, and enhances the electrochemical reactions.},
	booktitle = {Fuel {Cells}},
	author = {Reshetenko, T. V. and Kim, H. T. and Krewer, U. and Kweon, H. J.},
	year = {2007},
	keywords = {Direct methanol fuel cell, EIS, MEA preparation, Pt-Ru loading},
	pages = {238--245},
}

The influence of the Pt-Ru anode loading and MEA preparation techniques on direct methanol fuel cell (DMFC) performance is studied. Two different anode catalyst layer preparation techniques are employed. One is the direct coating of anode catalyst ink on a membrane to form a catalyst coated membrane, CCManode, and the other is the coating of the ink on the diffusion layers, which generates a catalyst coated substrate, CCSanode. The power density of a combined CCManode/CCScathode MEA is higher than for a CCSanode/CCScathode MEA. The main difference in the performance is observed in the high current density region, where two-phase flow is present and mass transfer processes govern the performance. The CCManode and CCSanode have different macroscopic structures, while showing the same microscopic morphology. Based on their morphological differences, it is expected that the combination of the CCManode and carbon paper provides the more homogeneous removal of CO2 at high currents. The authors suggest that the application of the CCManode with an optimal anode loading improves anode mass transfer, reduces methanol crossover, and enhances the electrochemical reactions.

@article{krewer_impedance_2006,
	title = {Impedance spectroscopic analysis of the electrochemical methanol oxidation kinetics},
	volume = {589},
	copyright = {All rights reserved},
	issn = {15726657},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S0022072806000763},
	doi = {10.1016/j.jelechem.2006.01.027},
	language = {en},
	number = {1},
	urldate = {2019-06-26},
	journal = {Journal of Electroanalytical Chemistry},
	author = {Krewer, U. and Christov, M. and Vidakovic’, T. and Sundmacher, K.},
	month = apr,
	year = {2006},
	pages = {148--159},
}

@article{schultz_systematic_2006,
	title = {Systematic analysis of the direct methanol fuel cell},
	volume = {37},
	copyright = {All rights reserved},
	issn = {0021-891X, 1572-8838},
	url = {http://link.springer.com/10.1007/s10800-006-9209-9},
	doi = {10.1007/s10800-006-9209-9},
	language = {en},
	number = {1},
	urldate = {2019-06-26},
	journal = {Journal of Applied Electrochemistry},
	author = {Schultz, T. and Krewer, U. and Vidaković, T. and Pfafferodt, M. and Christov, M. and Sundmacher, K.},
	month = dec,
	year = {2006},
	pages = {111--119},
}

@article{krewer_transfer_2006,
	title = {Transfer function analysis of the dynamic behaviour of {DMFCs}: {Response} to step changes in cell current},
	volume = {154},
	copyright = {All rights reserved},
	issn = {03787753},
	shorttitle = {Transfer function analysis of the dynamic behaviour of {DMFCs}},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S0378775305006117},
	doi = {10.1016/j.jpowsour.2005.04.006},
	language = {en},
	number = {1},
	urldate = {2019-06-26},
	journal = {Journal of Power Sources},
	author = {Krewer, U. and Sundmacher, K.},
	month = mar,
	year = {2006},
	pages = {153--170},
}

@article{krewer_direct_2004,
	title = {Direct methanol fuel cell ({DMFC}): analysis of residence time behaviour of anodic flow bed},
	volume = {59},
	copyright = {All rights reserved},
	issn = {00092509},
	shorttitle = {Direct methanol fuel cell ({DMFC})},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S0009250903004925},
	doi = {10.1016/j.ces.2003.09.029},
	language = {en},
	number = {1},
	urldate = {2019-06-26},
	journal = {Chemical Engineering Science},
	author = {Krewer, U. and Song, Y. and Sundmacher, K. and John, V. and Lübke, R. and Matthies, G. and Tobiska, L.},
	month = jan,
	year = {2004},
	pages = {119--130},
}

@article{krewer_pollution_2002,
	title = {Pollution {Prevention} through {Solvent} {Selection} and {Waste} {Minimization}},
	volume = {41},
	copyright = {All rights reserved},
	issn = {0888-5885, 1520-5045},
	url = {https://pubs.acs.org/doi/10.1021/ie020037n},
	doi = {10.1021/ie020037n},
	language = {en},
	number = {18},
	urldate = {2019-06-26},
	journal = {Industrial \& Engineering Chemistry Research},
	author = {Krewer, Ulrike and Liauw, Marcel A. and Ramakrishna, M. and Hari Babu, M. and Raghavan, K. V.},
	month = sep,
	year = {2002},
	pages = {4534--4542},
}