Effect of cobalt bis(dicarbollides) on electrochemical oxygen reduction on Pt electrode in methanol–acid solution

Abstract

Electrochemical oxygen reduction on a platinum electrode has been investigated in methanol–0.05 M H 2SO 4 aqueous solutions in the presence of acids of cobalt bis(dicarbollide) (H +B −, H +[(1,2-C 2B 9H 11) 2-3-Co] (−)) or its hexachlorinated derivative (H +BCl −, H + [(8,8′,9,9′,12,12′-Cl 6-(1,2-C 2B 9H 8) 2-3-Co)] (−)). Methanol oxidation was suppressed with H +BCl − significantly, and selective oxygen reduction was achieved on a platinum electrode. The efficiency of oxygen reduction to H 2O, which depended on the electrode potential, was lower by 2% to 20% than that without H +BCl −. The mechanism was investigated by surface-enhanced infrared absorption spectroscopy (SEIRAS). H +BCl − suppresses formation of both the catalytic poison, linear CO (ads.), from methanol and the formate, the intermediate of the non-CO path of methanol oxidation.