K-edge X-ray absorption fine structure analysis of Pt/Au core-shell electrocatalyst : evidence for short Pt-Pt distance

A carbon-supported Pt-shell Au-core electrocatalyst (Pt/Au/C) was prepared by sequential deposition of Pt ions on the surface of Au nanoparticles supported on carbon. The area-specific activity of the oxygen reduction reaction (ORR) for the prepared Pt/Au/C in 0.1 M HClO4, aqueous solution was approximately 2 times higher than that for a commercial carbon-supported Pt electrocatalyst (Pt/C). The core-shell structure was confirmed using electrochemical methods and Pt and Au K-edge X-ray absorption fine structure (XAFS) analysis. XAFS analyses indicated that the Pt-Pt bond distance for the Pt/Au/C catalyst was shorter than that for Pt foil and the Pt/C catalyst. In addition, the Au Au distance was much shorter than that for Au foil. The reason for the high ORR activity of Pt/Au/C is considered to be shorter Pt-Pt bond distance as compared to that of Pt/C