TY - JOUR A1 - Scherb, Tobias A1 - Kimber, S. A. J. A1 - Stephan, Christiane A1 - Henry, P. F. A1 - Schumacher, G. A1 - Escolástico, S. A1 - Serra, J. M. A1 - Seeger, J. A1 - Just, J. A1 - Hill, A.H. A1 - Banhart, J. T1 - Nanoscale order in the frustrated mixed conductor La5.6WO12-Delta N2 - This article reports a comprehensive investigation of the average and local structure of La5.6WO12-δ, which has excellent mixed proton, electron and oxide ion conduction suitable for device applications. Synchrotron X-ray and neutron powder diffraction show that a cubic fluorite supercell describes the average structure, with highly disordered lanthanum and oxide positions. On average, the tungsten sites are sixfold coordinated and a trace [3.7 (1.3)%] of anti-site disorder is detected. In addition to sharp Bragg reflections, strong diffuse neutron scattering is observed, which hints at short-range order. Plausible local configurations are considered and it is shown that the defect chemistry implies a simple 'chemical exchange' interaction that favours ordered WO6 octahedra. The local model is confirmed by synchrotron X-ray pair distribution function analysis and EXAFS experiments performed at the La K and W L-3 edges. It is shown that ordered domains of similar to 3.5 nm are found, implying that mixed conduction in La5.6WO12-δ is associated with a defective glassy-like anion sublattice. The origins of this ground state are proposed to lie in the nonbipartite nature of the face-centred cubic lattice and the pairwise interactions which link the orientation of neighbouring octahedral WO6 sites. This 'function through frustration' could provide a means of designing new mixed conductors. KW - neutron diffraction KW - x-ray diffraction KW - proton conductors PY - 2016 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-366756 DO - https://doi.org/10.1107/S1600576716006415 SN - 1600-5767 VL - 49 IS - Issue 3 SP - 997 EP - 1008 PB - International Union of Crystallography CY - Chester, UK AN - OPUS4-36675 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Krüger, P. A1 - Markötter, Henning A1 - Klages, M. A1 - Haußmann, J. A1 - Arlt, Tobias A1 - Riesemeier, Heinrich A1 - Hartnig, C. A1 - Banhart, J. A1 - Manke, I. A1 - Scholta, J. T1 - Dreidimensionale Untersuchung der Wasserverteilung in einer Miniatur-PEM-Brennstoffzelle KW - Resolution neutron-radiography KW - Local current distribution KW - Cells KW - Quantification PY - 2010 SN - 0025-5300 VL - 52 IS - 10 SP - 712 EP - 717 PB - Hanser CY - München AN - OPUS4-23044 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Markötter, Henning A1 - Alink, R. A1 - Haußmann, J. A1 - Dittmann, K. A1 - Arlt, Tobias A1 - Wieder, F. A1 - Tötzke, C. A1 - Klages, M. A1 - Reiter, C. A1 - Riesemeier, Heinrich A1 - Scholta, J. A1 - Gerteisen, D. A1 - Banhart, J. A1 - Manke, I. T1 - Visualization of the water distribution in perforated gas diffusion layers by means of synchrotron X-ray radiography N2 - Perforated gas diffusion layers (GDLs) of polymer electrolyte membrane fuel cells (PEMFCs) were investigated by means of in-situ synchrotron X-ray radiography during operation. We found a strong influence of perforations on the water distribution and transport in the investigated Toray TGP-H-090 GDL. The water occurs mainly around the perforations, while the holes themselves show varying water distributions. Some remain dry, while most of them fill up with liquid water after a certain period or might serve as drainage volume for effective water transport. KW - Polymer electrolyte membrane fuel cell (PEMFC) KW - Radiography KW - Synchrotron KW - X-ray imaging KW - Perforated gas diffusion layer (GDL) KW - Water transport PY - 2012 DO - https://doi.org/10.1016/j.ijhydene.2012.01.141 SN - 0360-3199 VL - 37 IS - 9 SP - 7757 EP - 7761 PB - Elsevier CY - Oxford AN - OPUS4-26434 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Markötter, Henning A1 - Manke, I. A1 - Haußmann, J. A1 - Arlt, Tobias A1 - Klages, M. A1 - Krüger, P. A1 - Hartnig, C. A1 - Scholta, J. A1 - Müller, Bernd R. A1 - Riesemeier, Heinrich A1 - Banhart, J. T1 - Combined synchrotron X-ray radiography and tomography study of water transport in gas diffusion layers N2 - Synchrotron X-ray radiography and tomography investigations of a custom-made polymer electrolyte membrane fuel cell optimised for visualisation purposes are presented. The 3D water distribution and transport pathways in the porous carbon fibre gas diffusion layers (GDLs) were investigated. The authors found that water is not only moving from the GDL into the channel, but can also take the opposite way, that is, from the channel into free pore space of the GDL. Such movement of water into the opposite direction has been subject of speculations but has so far not yet been reported and might bring new insights into the general water transport behaviour, which might give new aspects to the general description of water transport processes and influence modelling assumptions to describe the process taking place in the GDL. KW - Synchrotron radiography KW - Synchrotron tomography KW - Gas diffusion layers KW - Water transport PY - 2012 DO - https://doi.org/10.1049/mnl.2012.0410 SN - 1750-0443 VL - 7 IS - 7 SP - 689 EP - 692 PB - IET CY - London AN - OPUS4-26282 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Markötter, Henning A1 - Haußmann, J. A1 - Alink, R. A1 - Dittmann, K. A1 - Tötzke, C. A1 - Krüger, P. A1 - Klages, M. A1 - Arlt, Tobias A1 - Müller, Bernd R. A1 - Riesemeier, Heinrich A1 - Scholta, J. A1 - Gerteisen, D. A1 - Manke, I. A1 - Banhart, J. T1 - Investigation of fuel cell materials and liquid water transport by means of synchrotron imaging N2 - Synchrotron imaging allows addressing various important issues in fuel cell research, for example water distribution and transport. The water distribution in polymer electrolyte membrane fuel cells (PEMFCs) was observed quasi in-situ directly after operation by means of synchrotron tomography. The 3D data set was compared with the tomogram of a dry cell in order to separate the water distribution from cell materials. Engineered transport pathways realized by perforating holes through the gas diffusion layer (GDL) are a recent approach to optimize water transport and cell performance. For some parameter sets a cell performance increase and an improvement of stabilization have already been proven. We present high resolution investigations of the water distribution in perforated GDLs of operating PEMFCs by means of in-situ synchrotron radiography. The surrounding areas of the holes exhibited a distinct hydrophilic character. KW - Gas-diffusion layers KW - Resolution neutron-radiography KW - X-ray radiography KW - Visualization KW - PEMFC PY - 2013 DO - https://doi.org/10.1149/04529.0195ecst SN - 1938-6737 SN - 1938-5862 VL - 45 IS - 29 SP - 195 EP - 202 CY - Pennington, NJ, USA AN - OPUS4-30545 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Markötter, Henning A1 - Manke, I. A1 - Krüger, P. A1 - Arlt, Tobias A1 - Huassmann, J. A1 - Klages, M. A1 - Riesemeier, Heinrich A1 - Hartnig, C. A1 - Scholta, J. A1 - Banhart, J. T1 - Investigation of 3D water transport paths in gas diffusion layers by combined in-situ synchrotron X-ray radiography and tomography N2 - The three-dimensional water distribution and water transport paths in the gas diffusion layer (GDL) and the adjacent micro-porous layer (MPL) of a polymer electrolyte membrane fuel cell (PEMFC) were analyzed during cell operation. The technique of quasi in-situ X-ray tomography was used for a 3D visualization of the water distribution and the structure of the GDL at different operating conditions. Based on findings from in-situ radiographic measurements water transport paths were detected and subsequently examined by tomography. The combination of these 2D and 3D techniques allows for a fully three-dimensionally resolved visualization of transport paths through the GDL. KW - Polymer electrolyte membrane fuel cell (PEMFC) KW - Radiography KW - Tomography KW - Synchrotron X-ray imaging KW - Gas diffusion layer (GDL) KW - Water transport paths PY - 2011 DO - https://doi.org/10.1016/j.elecom.2011.06.023 SN - 1388-2481 VL - 13 IS - 9 SP - 1001 EP - 1004 PB - Elsevier B.V. CY - Amsterdam AN - OPUS4-25244 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Markötter, Henning A1 - Haußmann, J. A1 - Alink, R. A1 - Tötzke, C. A1 - Arlt, Tobias A1 - Klages, M. A1 - Riesemeier, Heinrich A1 - Scholta, J. A1 - Gerteisen, D. A1 - Banhart, J. A1 - Manke, I. T1 - Influence of cracks in the microporous layer on the water distribution in a PEM fuel cell investigated by synchrotron radiography N2 - Water evolution in the gas diffusion layer of a polymer electrolyte membrane fuel cell was visualized in situ by means of synchrotron X-ray radiography. Cracks in the microporous layer were identified as start points of efficient liquid water transfer paths through the gas diffusion layer. Quantitative analysis of the water flow rate through those arbitrarily distributed cracks into the gas channel revealed that they have a strong influence on the overall liquid water transport. This could find entry into future material design and simulation. KW - Polymer electrolyte membrane fuel cell (PEMFC) KW - Radiography KW - Synchrotron X-ray imaging KW - Microporous layer (MPL) KW - Water transport KW - Liquid water flow rate PY - 2013 DO - https://doi.org/10.1016/j.elecom.2013.04.006 SN - 1388-2481 VL - 34 SP - 22 EP - 24 PB - Elsevier CY - Amsterdam AN - OPUS4-30548 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Arlt, Tobias A1 - Klages, M. A1 - Messerschmidt, M. A1 - Riesemeier, Heinrich A1 - Scholta, J. A1 - Banhart, J. A1 - Manke, I. T1 - Influence of artificial aging of gas diffusion layers on the water management of PEM fuel cells N2 - The influence of artificial aging of gas diffusion layers (GDL) on the water management within the GDL was investigated in-operando by synchrotron X-ray radiography. One GDL was subjected to an accelerated aging procedure in 30% H2O2 solution, while another GDL was pristine. Radiographic measurements were combined with temporally resolved electrical analyzes. Significant differences in cell voltage and water accumulation were observed during cell operation at steady-state conditions. The cell which contained the aged GDL featured a higher water amount especially at the anode side and a lower cell voltage. KW - Degradation KW - Liquid water PY - 2014 DO - https://doi.org/10.1149/2.004402eel SN - 2162-8726 VL - 3 IS - 2 SP - F7 EP - F9 PB - ECS CY - Pennington, NJ, USA AN - OPUS4-32410 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Arlt, Tobias A1 - Manke, I. A1 - Wippermann, K. A1 - Schröder, A. A1 - Mergel, J. A1 - Riesemeier, Heinrich A1 - Banhart, J. T1 - Röntgen-Kanten-Tomografie und -Radiografie zur Untersuchung von Alterungseffekten in Brennstoffzellenmaterialien KW - Resolution neutron-radiography KW - Local current distribution KW - Water transport KW - Carbon-dioxide KW - Methanol KW - Platinum KW - Oxidation PY - 2010 SN - 0025-5300 VL - 52 IS - 10 SP - 692 EP - 697 PB - Hanser CY - München AN - OPUS4-23045 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hartnig, C. A1 - Manke, I. A1 - Schloesser, J. A1 - Krüger, P. A1 - Kuhn, R. A1 - Riesemeier, Heinrich A1 - Wippermann, K. A1 - Banhart, J. T1 - High resolution synchrotron X-ray investigation of carbon dioxide evolution in operating direct methanol fuel cells N2 - The carbon dioxide evolution and bubble formation in an operating fuel has been studied by means of synchrotron X-ray radiography. Two different observation directions have been chosen: a through-plane insight has been employed to track the formation of bubbles starting at the corner of the lands of the flow field; a depth profile of the carbon dioxide evolution has been derived from cross sectional studies describing an affected area of up to 100 µm. The dynamics of the bubble formation and detachment of the bubbles from the position of formation is strongly correlated with the current density. Cracks and breaks in the catalyst layer which result from the preparation process are visible under operating conditions and a possible swelling of the catalyst layer does not reach a complete vanishing of the cracks. KW - DMFC KW - Carbon dioxide evolution KW - Synchrotron radiography KW - In situ study KW - Cross section KW - Through-plane PY - 2009 DO - https://doi.org/10.1016/j.elecom.2009.05.047 SN - 1388-2481 VL - 11 IS - 8 SP - 1559 EP - 1562 PB - Elsevier CY - Amsterdam AN - OPUS4-20577 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Maier, W. A1 - Arlt, Tobias A1 - Wannek, C. A1 - Manke, I. A1 - Riesemeier, Heinrich A1 - Krüger, P. A1 - Scholta, J. A1 - Lehnert, W. A1 - Banhart, J. A1 - Stolten, D. T1 - In-situ synchrotron X-ray radiography on high temperature polymer electrolyte fuel cells N2 - In contrast to classical low temperature polymer electrolyte fuel cells (LT-PEFCs), the membrane conductivity in high temperature polymer electrolyte fuel cells (HT-PEFCs) (operating temperature ~ 160 °C) is based on proton transport within phosphorus-oxygen acids at different levels of hydration, orthophosphoric acid (H3PO4) being the simplest example. We present for the first time in-situ synchrotron X-ray radiography measurements applied to a HT-PEFC to gain insight into the local composition of the membrane electrode assembly (MEA) under dynamic operating conditions. Transmission changes during the radiographic measurements exhibit a clear influence of the formation of product water on the membrane composition. KW - HT-PEFC KW - Synchrotron x-ray radiography KW - Membrane electrode assembly (MEA) KW - Phosphoric acid PY - 2010 DO - https://doi.org/10.1016/j.elecom.2010.08.002 SN - 1388-2481 VL - 12 IS - 10 SP - 1436 EP - 1438 PB - Elsevier CY - Amsterdam AN - OPUS4-23962 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -