Two-dimensional spatial mapping of Pt chemical species of Pt/C cathode catalysts in polymer electrolyte fuel cell (PEFC) membrane electrode assembly (MEA) was achieved to gain new insights into the place and mechanism for Pt oxidation and degradation of the Pt/C cathode catalyst as the key issues of PEFC performances and durability by a new 2D nano-focused beam XAFS mapping technique. The MEA Pt/C catalysts were also characterized by STEM-EDS. The nano-XANES white line peak intensity revealed that the Pt/C catalyst was oxidized to Pt2+ species by durability test cycles. Particularly in the crack region near the polymer electrolyte, the Pt nanoparticles were preferentially oxidized as proved by the nano XAFS (XANES and EXAFS). Small Pt clusters were also observed in the crack. The white line peak intensity also became maximum in the intermediate region between the cathode layer edge and Pt band. This study is the first to succeed in observing the spatial distribution of Pt2+ ions and small Pt clusters, which may be relevant to ionization and leaching of Pt nanoparticles from the cathode catalyst layer.

2D spatial mapping of Pt chemical species in Pt/C cathode catalysts in polymer electrolyte fuel cells by a nano-beam XAFS technique

248th National Meeting (2014)

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