Electrocatalytic activities of some codeposited binary noble metal surfaces over carbon substrates for anodic oxidation of methanol in alkaline medium: Part II - Palladium-noble metal codeposits

Abstract

Electrocatalytic activities of codeposited binary Pd-Rh, Pd-Ru, Pd-Ir and Pd-Au metal surfaces of various compositions over carbon substrate for anodic oxidation of methanol in alkaline medium at 25°C have been evaluated. It is observed that the electrocatalytic activity of C/Pd electrode is drastically enhanced by codeposition with the other noble metals, magnitude of enhancement passing through a maximum at a composition, θ<img src='http://www.niscair.res.in/jinfo/equation166.gif' border=0>, characteristic of the binary noble metal combination. The observed enhancement is also different for different cometals, their order at the respective θ<img src='http://www.niscair.res.in/jinfo/equation166.gif' border=0> being Rh > Ru > Au > Ir. Extrapolation of the well known 'bifunctional theory' of electrocatalysis by binary noble metal alloys to these binary codeposits is partially successful in explaining the observed electrocatalytic properties. The activities appear to arise from the geometric as well as electronic properties of the binary combines.