Monolayer-level Ru- and NbO2-Supported platinum electrocatalysts for methanol oxidation

We developed electrocatalysts with a monolayer-level Pt content for methanol oxidation by depositing Pt or Pt+M (M = Os, Ir, Rh, Pd) on the surfaces of Ru nanoparticles through the galvanic replacement of Cu adlayers and by chemically reducing Pt ions on a NbO2 oxide surface. Compared with a commercial PtRu/C alloy catalyst, the electrocatalyst with a monolayer of Pt (Pt-ML/Ru/C) showed three times higher Pt mass activity and improved durability for methanol oxidation. The activity originates from the efficient bifunctional mechanism as well as the electronic effect that weakens the Pt-CO bonding facilitated by optimized size of Pt-free and Pt-covered Ru support. Electrocatalysts comprising mixed-metal M+Pt on Ru nanoparticles also had higher activity than the commercial one but did not surpass the Pt-ML/Ru/C electrocatalyst. The properties of the electrocatalysts composed of a monolayer amount of Pt deposited on niobium oxide nanoparticles indicate that NbO2 holds considerable promise as a support for a Pt monolayer for methanol oxidation. (c) 2007 The Electrochemical Society.