Optimum surface composition of platinum-ruthenium nanoparticles and sputter-deposited films for methanol oxidation reaction

Abstract

The methanol oxidation activity of platinum-ruthenium nanoparticles on carbon supports and sputter-deposited films was investigated as a function of the surface composition. A technique combining the copper under-potential deposition and copper stripping was used to measure the surface platinum-ruthenium composition. The measurements showed that the surface composition was not always the same as the bulk composition even though an X-ray diffraction analysis showed that the platinum-ruthenium formed a solid-solution. Liner sweep voltammetry was used to measure the methanol oxidation activity in a 0.5 mol/L sulfuric acid solution containing 1.0 mol/ L methanol at 308 K. The result from this electrochemical analysis showed that the methanol oxidation activity correlated with the surface platinum-ruthenium composition. The optimum surface composition was different between the nanoparticles and the films. The value for the nanoparticles was around 50 at% ruthenium, while for the films that was around 25 at % ruthenium.