During start-up and shut-down processes in polymer electrolyte fuel cells (PEFCs) for automobiles the feed gases should be exchanged; for example, at the anode the feed gas is exchanged from air to H2 or from H2 to air. When the anode feed gas is exchanged while keeping the cathode under air, the potential applied to the cell changes rapidly and the Pt/C cathode catalyst degradation occurs. To investigate the origin and mechanism of the catalyst degradation, we measured the structural and electronic changes of the Pt/C cathode catalyst during the anode gas exchange (AGEX) cycles (H2 -> air -> H2 ->�) by means of in situ time-resolved XAFS technique.The Pt LIII-edge white line peak intensity changed during the AGEX cycles, depending on the place of MEA. The transient response XAFS measurements in the potential change from 0.4 V to 1.4 V were also performed in the course of the AGEX cycles. The kinetic constants for the Pt valence changes and structural transformations were determined and compared to the electrochemical degradation results by the AGEX cycles. The dynamic XAFS results provided new insights into the key issues and mechanism for the degradation of MEA Pt/C cathode catalysts by increasing AGEX cycles.

Origin and mechanism of Pt/C cathode catalyst degradation in polymer electrolyte fuel cell by anode gas exchange cycles studied by in situ time-resolved XAFS

248th National Meeting (2014)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.