METHANOL ELECTROOXIDATION ON UNSUPPORTED PT-RU ALLOYS AT DIFFERENT TEMPERATURES

A wide compositional range of unsupported platinum-ruthenium alloy cat alysts were prepared by thermal decomposition of the chlorides and chl oroacids. The electrocatalysts were characterized by cyclic voltammetr y, x-ray diffraction, and energy-dispersive x-ray spectroscopy. The BE T surface area of the electrocatalysts increases with increasing Ru co ntent up to similar to 70 atomic percent (a/o) and then reaches a plat eau value. Electrodes fabricated from the electrocatalysts were also e valuated as anodes for methanol electro-oxidation in sulfuric acid ove r a range of temperatures. Unlike the situation for pure Pt, Ru is ina ctive for methanol electro-oxidation at 25 degrees C but becomes activ e at higher temperatures. The peak current observed during an anodic p otential scan gradually shifts to more cathodic potentials with increa sing 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 2 5 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 P t-Ru (similar to 50.50) electrode.