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Koizumi S, Ueda S, Inada T, Noda Y, Robinson RA. Microstructure and water distribution in catalysts for polymer electrolyte fuel cells, elucidated by contrast variation small-angle neutron scattering. J Appl Crystallogr 2019. [DOI: 10.1107/s1600576719008343] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
By using small-angle neutron scattering (SANS) reinforced by scanning electron microscopy, the fine structure of catalysts for polymer electrolyte fuel cells has been investigated. The experimental data resulting from contrast variation with mixed light and heavy water (H2O/D2O) are well described by a core–shell model with fluctuations in concentration between water and Nafion. In particular, SANS obtained with the mixed water ratio 30/70, which corresponds to a matching point between mixed water and Nafion, shows a broad scattering maximum, which is attributed to a 5 nm-thick Nafion shell on the surface of the larger carbon particles. After swelling by water, the ionomer layer absorbs water at the 17 wt% level. By changing the H2O/D2O ratio, it was further confirmed that the catalyst with the ionomer exhibits water repellence, whereas the bare catalyst without the ionomer is wetted by water. Because it is very difficult to extract more information, for instance regarding the Pt–Nafion interactions, by means of small-angle scattering, reflectometry and grazing-incidence scattering experiments with neutrons should be attempted on a model catalyst prepared on a flat substrate.
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Lin Y, Arlt T, Kardjilov N, Manke I, Lehnert W. In Operando Neutron Radiography Analysis of a High-Temperature Polymer Electrolyte Fuel Cell Based on a Phosphoric Acid-Doped Polybenzimidazole Membrane Using the Hydrogen-Deuterium Contrast Method. Energies 2018; 11:2214. [DOI: 10.3390/en11092214] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In order to characterize high temperature polymer electrolyte fuel cells (HT-PEFCs) in operando, neutron radiography imaging, in combination with the deuterium contrast method, was used to analyze the hydrogen distribution and proton exchange processes in operando. These measurements were then combined with the electrochemical impedance spectroscopy measurements. The cell was operated under different current densities and stoichiometries. Neutron images of the active area of the cell were captured in order to study the changeover times when the fuel supply was switched between hydrogen and deuterium, as well as to analyze the cell during steady state conditions. This work demonstrates that the changeover from proton to deuteron (and vice versa) leads to local varying media distributions in the electrolyte, independent of the overall exchange dynamics. A faster proton-to-deuteron exchange was re-discovered when switching the gas supply from H2 to D2 than that from D2 to H2. Furthermore, the D2 uptake and discharge were faster at a higher current density. Specifically, the changeover from H to D takes 5–6 min at 200 mA cm−2, 2–3 min at 400 mA cm−2 and 1–2 min at 600 mA cm−2. An effect on the transmittance changes is apparent when the stoichiometry changes.
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Page KA, Dura JA, Kim S, Rowe BW, Faraone A. Neutron Techniques as a Probe of Structure, Dynamics, and Transport in Polyelectrolyte Membranes. Neutron Scattering Applications and Techniques 2015. [DOI: 10.1007/978-3-319-06656-1_10] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
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Ueda S, Kobayashi Y, Koizumi S, Tsutsumi Y. In situobservation of water in a fuel cell catalyst using scanning electron microscopy. Microscopy (Oxf) 2014; 64:87-96. [DOI: 10.1093/jmicro/dfu100] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2014] [Accepted: 10/27/2014] [Indexed: 11/13/2022] Open
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