KINETICS OF HYDROGEN EVOLUTION REACTION FROM AQUEOUS HCLO4 SOLUTIONS ON SOME CODEPOSITED BINARY NOBLE-METAL SURFACES OVER PT-SUBSTRATES BY CYCLIC VOLTAMMETRY

Relative electrocatalytic activities of some codeposited binary noble metal surfaces over Pt-substrates [(Pt)M1-M2] with different compositions of M1 = Pt and M2 = Pd, Ir and Au and M1 = Pd and M2 = Ir and Au have been studied for hydrogen evolution reaction (HER) from aqueous HClO4 solutions by determining the rate constant k(s) of the reaction by cyclic voltammetry. The k(s) values have been determined by Shain and Nicholson's formulations from the observed quasi-reversible cyclic voltammograms (CVG's) obtained at different scan rates ranging from 0.002 to 0.3 V s-1 in the potential range 0 to -1.0 V. The observed k(s) - M2 composition profiles of [(Pt)M1-M2] surfaces in both the cases with M1 = Pt or Pd are found to pass through a minimum presumably because of the enhanced coverage of the surfaces by nascent hydrogen, theta(H), and the consequent decrease of the fraction of free surface, which seemingly dictates the rate of HER in the resent cases.