Methanol oxidation on PtRu electrodes. Influence of surface structure and Pt-Ru atom distribution

The activities of different types of PtRu catalysts for methanol oxidation are compared. Materials used were: UHV-cleaned PtRu alloys, UHV-evaporated Ru onto Pt(lll) as well as adsorbed Ru on Pt(lll) prepared with and without additional reduction by hydrogen. Differences in the catalytic activity ar e observed to depend on the preparation procedure of the catalysts. The dep endence of the respective catalytic activities upon the surface composition is reported. UHV-STM data for Pt(111)/Ru show the formation of two- and th ree-dimensional structures depending on surface coverage. A molecular insig ht on the electrochemical reaction is given via in situ infrared spectrosco py. Analysis of the data indicates that the most probable rate-determining step is the reaction of adsorbed CO with Ru oxide.