Methanol Electro‐oxidation on Unsupported Pt‐Ru Alloys at Different Temperatures

Abstract

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 ∼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°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 ∼50 a/o ruthenium electrocatalyst provides the highest activity for methanol electro‐oxidation at both 25 and 60°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 (∼50:50) electrode.