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

Abstract

Electrocatalytic activities of binary noble metal codeposits Pt-Pd, Pt-Rh, Pt-Ru, Pt-Ir and Pt-Au of different compositions over carbon substrate have been studied for the anodic oxidation of methanol in alkaline medium. Galvanostatic steady state and slow sweep cyclic voltammetric methods in conjunction with chronopotentiometric estimation of roughness factor (R_f) and examination of the geometric properties of the electrodes from scanning electron micrographs (SEM) are employed. Catalytic activities of these binary deposits are better than the Pt-deposited electrode. The electrocatalytic activities reach a maximum at a particular composition depending on the cometal, the order being: Rh &gt; Ru &gt;Pd &gt; Ir &gt; Au. The peak current density (<em>i</em>_p) and roughness factor (R_f) values also exhibit similar type of variations with maxima lying at the composition of maximal activities. The observed enhancement of catalytic activities of C/Pt electrodes with addition of cometals can be explained with the help of well known 'bi-functional theory' of alloy electrocatalysts. A careful analysis of the results, in particular the SEM's, reveal that while the extrinsic geometric properties are very much responsible for the observed activities, intrinsic electronic properties of the codeposits are equally important.