In situ X-ray absorption studies of a Pt-Ru electrocatalyst

X-ray absorption studies (XAS) were done on a carbon supported Pt-Ru electrocatalyst in 1 M HClO{sub 4}. Results at the Pt L{sub 3} and L{sub 2} and edges confirmed that the Pt was alloyed with Ru and that the Ru content was about 25 atomic percent. There was a large excess of unalloyed Ru, with only about 10% of the Ru alloyed with the Pt. The Pt XAS indicated that the Ru increased that Pt d band vacancies and decreased the Pt-Pt bond distances from 2.77 {angstrom} to values between 2.71 and 2.73 {angstrom}. The bifunctional mechanism for methanol oxidation on Pt-Ru electrocatalysts needs to be modified to account for the effect of these electronic changes on the adsorption of H and CO residues from methanol decomposition. There are significant changes in the Pt XAS in going from the reversible hydrogen potential to 0.24 V. This may be due to the onset of the formation of RuOH species on the alloy. Further fine tuning of the electronic structure and the electrocatalysis may be possible through the use of ternary alloys.