Characterization of Dealloyed Catalysts in PEMFC

Pt-alloy catalysts have attracted much attention because of their high activity for the oxygen reduction reaction compared to that of pure Pt catalysts. One variant of the Pt-alloy catalyst is the “dealloyed catalyst” made by first preparing an alloy precursor with a high base-metal-to-Pt ratio (≥1:1) and then removing most of the base metal, resulting in Pt-rich particles (M:Pt of ~1:3).¹ Removal of the base metal (dealloying) by electrochemical voltage cycling or by acid leaching can result in a particle with Pt-rich skin covering a base-metal-rich core. It was suggested that lattice mismatch between the two layers induced strain in the surface Pt shell² and that the near-surface structure was a driving factor in determining the initial activity³. We have generated a set of catalysts with very similar initial activity but vastly different durability under fuel cell testing.⁴

These catalysts were characterized using high-resolution TEM and extended X-ray absorption spectroscopy.  In this talk we will summarize the factors that appear to have significant affects on their activities and durability.  Electrode development using the improved catalysts will also be discussed.