Methanol electro-oxidation on unsupported Pt-Ru alloys at different temperatures

A wide compositional range of unsupported platinum-ruthenium alloy catalysts were prepared by thermal decomposition of the chlorides and chloroacids. The electrocatalysts were characterized by cyclic voltammetry, x-ray diffraction, and energy-dispersive x-ray spectroscopy. The BET surface area of the electrocatalysts increases with increasing Ru content up to similar to 70 atomic percent (a/o) and then reaches a plateau value. Electrodes fabricated from the electrocatalysts were also evaluated as anodes for methanol electro-oxidation in sulfuric acid over a range of temperatures. Unlike the situation for pure Pt, Ru is inactive for methanol electro-oxidation at 25 degrees C but becomes active at higher temperatures. The peak current observed during an anodic potential scan gradually shifts to more cathodic potentials with increasing temperature. When a comparison is made on the basis of electrode geometric surface area, a similar to 50 a/o ruthenium electrocatalyst provides the highest activity for methanol electro-oxidation at both 25 and 60 degrees C. The methanol electro-oxidation rate is 0.5 orders with respect to methanol concentration (between 0.1 and 2 M) for the Pt-Ru (similar to 50.50) electrode.