Journal
JOURNAL OF THE ELECTROCHEMICAL SOCIETY
Volume 166, Issue 4, Pages F198-F207Publisher
ELECTROCHEMICAL SOC INC
DOI: 10.1149/2.0371904jes
Keywords
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Funding
- U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy [DE-EE0007271]
- DOE Office of Science [DE-AC02-06CH11357]
- NSF Graduate Research Fellowship [DGE-1650441]
- NSF MRSEC program [DMR 1719875]
- NSF MRI grant [DMR 1429155]
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Maintaining high performance after extensive use remains a key challenge for low-Pt proton exchange membrane fuel cells for transportation applications. Strategically improving catalyst durability requires better understanding of the relationship between degradation mechanisms and catalyst structure. To investigate the effects of the carbon support morphology, we compare the electrochemical performance and durability of membrane electrode assemblies (MEAs) using Pt and PtCox catalysts with a range of porous, solid, and intermediate carbon supports (HSC, Vulcan, and acetylene black). We find that electrochemical surface area (ECSA) retention after a catalyst-targeted durability test tends to improve with increasing support porosity. Using electron microscopy, we investigate microstructural changes in the catalysts and reveal the underlying degradation mechanisms in MEA specimens. Pt migration to the membrane and catalyst coarsening, measured microscopically, together were quantitatively consistent with the ECSA loss, indicating that these were the only two significant degradation pathways. Changes in catalyst particle size, morphology, and PtCo core-shell structure indicate that Ostwald ripening is a significant coarsening mechanism for catalysts on all carbons, while particle coalescence is only significant on the more solid carbon supports. Porous carbon supports thus appear to protect against particle coalescence, providing an effective strategy for mitigating catalyst coarsening. (C) The Author(s) 2019. Published by ECS.
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