HIGHLY-ACTIVE ELECTROCATALYSIS BY COBALT TETRAPHENYLPORPHYRIN INCORPORATED IN A NAFION MEMBRANE FOR PROTON REDUCTION

Electrocatalytic Hf reduction tons studied with cobalt tetraphenylporp hyrin (CoTPP) incorporated in a Nafion membrane coated on a Pt electro de (denoted as Pt/Nf[CoTPP]). It was found that Pt/Nf[CoTPP] shows an efficient catalytic activity to produce H-2 around the theoretical H+/ H-2 redox potential (-0.25 V v. Ag/AgCl in a pH 1.01 aqueous solution) , and that its catalytic activity is remarkably higher than a neat CoT PP film and a conventional Pt catalyst. The amount of the H2 produced decreased with increasing CoTPP concentration in the membrane ([CoTPP] (Nf)]). The ratio of electroactive (CoTPP)-T-II was independent of its concentration, showing that the present electron transfer process tak es place via physical diffusion of the molecule. The intrinsic turnove r number (TNint) of the CoTPP to produce H-2, based on the electroacti ve amounts of the CoTPP, decreased with increasing [CoTPP](Nf). The ca talysis was discussed in terms of the characteristic of the Nafion mem brane. (C) 1998 John Wiley & Sons, Ltd.