Promotion by hydrous ruthenium oxide of platinum for methanol electro-oxidation

Pt–(RuOxHy)m electrocatalysts (m being the atomic Ru/Pt ratio) supported on multi-walled carbon nanotubes, in which amorphous hydrous ruthenium oxide (RuOxHy) is the exclusive Ru-containing species, were prepared and comprehensively characterized by X-ray diffraction, X-ray photoelectron spectroscopy, temperature-programmed reduction, thermogravimetric analysis and transmission electron microscopy techniques. Cyclic voltammetry (CV) and chronoamperometry studies of CO stripping and methanol electro-oxidation indicated that the CO tolerance and catalytic activity of Pt improved remarkably by the co-presence of RuOxHy. Repeated CV pretreatments in 0.5 M H2SO4 up to potentials higher than 0.46 V (vs. SCE) induced significant dissolution of RuOxHy, which changed the RuOxHy content, Pt–RuOxHy proximity and surface structure of Pt, and consequently altered the electrocatalytic activity of Pt in the final electrode. However, RuOxHy dissolution was not identified when the pretreatment potentials was set no higher than 0.46 V. Discussion on the promotional function of RuOxHy was made based on the peculiarity of RuOxHy as a mixed electron/proton conductor.