Identification of liquid water constraints in micro polymer electrolyte fuel cells without gas diffusion layers

Seyfang, Bernhard C.; Boillat, Pierre; Simmen, F.; Hartmann, Stefan; Frei, G.; Lippert, Thomas; Scherer, Guenther G.; Wokaun, Alexander

doi:10.1016/j.electacta.2009.12.061

Cited by 20 publications

(14 citation statements)

References 30 publications

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“…Proton-exchange membranes (PEMs), serving as proton-conductive media in PEMFCs, still need to be improved not only toward higher proton conductivity but also toward higher thermal and chemical durability. , Many physical/chemical phenomena are involved in the operation of PEMFCs, and the distribution and transport behavior of water species inside the PEMs are known to exert a large influence on these phenomena . Water transport in PEMFCs, such as the back-diffusion and electro-osmotic drag, as well as the water transport at the membrane/catalyst layer (CL) interfaces, is found to have a significant impact on both the performance and stability. , Nafion, a perfluorinated sulfonic acid polymer, is the most commonly used PEM for PEMFCs, and its water distribution has been extensively studied using various techniques, including vibrational spectroscopies, − nuclear magnetic resonance, neutron scattering/imaging, and X-ray scattering . Raman spectroscopy is a powerful technique for quantifying the distribution of water without interfering with the cell reaction. − Not only the distribution of the number of water molecules but also their chemical states inside the PEM are highly important.…”

Section: Introductionmentioning

confidence: 99%

Dynamic Distribution of Chemical States of Water inside a Nafion Membrane in a Running Fuel Cell Monitored by Operando Time-Resolved CARS Spectroscopy

et al. 2020

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The distribution and the chemical states of water in the electrolyte membrane of proton-exchange membrane fuel cells (PEMFCs) directly affect the performance and stability during cell operation. Coherent anti-Stokes Raman scattering (CARS) spectroscopy was used to investigate the transient behavior of water inside a Nafion membrane with a high time resolution of 0.5 s. After a current-density jump from 0.1 to 1.0 A cm −2 , the cell voltage rapidly dropped, then increased, and reached equilibrium in 7 s, whereas the ohmic resistance immediately dropped due to the increase in the water species that contributed significantly to the proton conductivity. The number of water molecules per sulfonic acid group, λ, at the membrane surface of the cathode side initially overshot and reached equilibrium after 7 s. This synchronous change of the cell voltage and λ is suggested to be caused by the change in oxygen partial pressure near the catalyst layer. This CARS technique is expected to be useful for analyzing many transient phenomena in materials science.

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Section: Introductionmentioning

confidence: 99%

Dynamic Distribution of Chemical States of Water inside a Nafion Membrane in a Running Fuel Cell Monitored by Operando Time-Resolved CARS Spectroscopy

et al. 2020

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“…(14)(15)(16)(17)20)) show that valuable results are still to be obtained with "conventional" through plane imaging, the focus was placed ECS Transactions, 41 (1) 27-38 (2011) 10.1149/1.3635541 © The Electrochemical Society 27 ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address.…”

Section: High Resolution Time Resolved Neutron Imaging Of Pefcsmentioning

confidence: 99%

Application of Neutron Imaging in PEFC Research

Boillat¹,

Oberholzer²,

Perego³

et al. 2011

ECS Trans.

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Recent work at PSI based on anisotropic resolution improvement allowed reaching a combination of 20 ȝm of effective spatial resolution with 10 s exposure times for neutron imaging. This new setup was applied to dynamic in plane imaging of PEFCs in different applications such as the characterization of bulk and interfacial water transport parameters of membranes using 1 H-2 H contrast imaging, the study of water/ice behavior during sub-zero startup, and the correlation between water accumulation and diffusive voltage loss by combining neutron imaging with transient Helox operation. Future studies will take advantage of a new setup allowing the simultaneous operation and neutron imaging of 6 small scale differential cells. IntroductionThe present paper describes the recent and future work at PSI in terms of application of neutron imaging to the study of water transport in polymer electrolyte fuel cells (PEFCs). Neutron imaging has been increasingly used for this purpose during the past decade (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19). The characteristics that make neutron imaging attractive for PEFC research in comparison to other imaging methods are: -The good transparency of usual fuel cell construction materials to neutrons -The high contrast of liquid water.-The negligible effects of neutron radiation (no heat absorbed, no radiation damage).-For specific experiments, the isotopic sensitivity of neutron imaging can be used. The first section of the paper will summarize PSI studies using neutron imaging that have recently been published or are in the process of publication. In the second section, the result of a yet unpublished study about the combination of neutron imaging with transient Helox operation will be presented in more detail. The possibilities opened by the latest improvements in detector and fuel cell test setup will be presented in a third section. Recent Work at PSI in Neutron Imaging of PEFCs High Resolution Time Resolved Neutron Imaging of PEFCsAlthough the recent record of publications (e.g. (14)(15)(16)(17)20)) show that valuable results are still to be obtained with "conventional" through plane imaging, the focus was placed ECS Transactions, 41 (1) 27-38 (2011) 10.1149/1.3635541 © The Electrochemical Society 27 ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 137.99.43.51 Downloaded on 2015-06-21 to IPat PSI in the recent years on high resolution imaging of fuel cells in in plane configuration (membrane parallel to the beam axis). Until recently, no imaging setups with sufficient spatial resolution for effectively observing the water distribution across a state-of-the-art fuel cell gas diffusion layer were available. Application to fuel cell imaging has been one of the main driving forces for realizing high resolution neutron imaging setups. The approach used at PSI consists in a setup with optimized optics and detector materials (21), combined with specific improvements targeting the applic...

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“…The geometry of the employed flow-fields is a meander that has 11 channels at the gas inlets. Along the flow, the channels are merged to six and finally to three channels, in order to ensure regular water removal [42]. The micro fuel cell was investigated using neutron radiography, which is a powerful method to identify liquid water in operating PEFCs [43,44].…”

Section: Neutron Imaging Of the Miniaturized Glassy Carbon Pefcmentioning

confidence: 99%

2+1D modelling of a polymer electrolyte fuel cell with glassy-carbon microstructures

Schumacher

Eller

Sartoris

et al. 2012

Mathematical and Computer Modelling of Dynamical Systems

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Identification of liquid water constraints in micro polymer electrolyte fuel cells without gas diffusion layers

Cited by 20 publications

References 30 publications

Dynamic Distribution of Chemical States of Water inside a Nafion Membrane in a Running Fuel Cell Monitored by Operando Time-Resolved CARS Spectroscopy

Dynamic Distribution of Chemical States of Water inside a Nafion Membrane in a Running Fuel Cell Monitored by Operando Time-Resolved CARS Spectroscopy

Application of Neutron Imaging in PEFC Research

2+1D modelling of a polymer electrolyte fuel cell with glassy-carbon microstructures

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