Oxygen electroreduction on gold-cobalt oxide binary nanocluster catalysts

The electroreduction of oxygen was investigated on mixed gold-cobalt oxide (Au/CoOx) nanoclusters in potassium hydroxide solution. Au/CoOx binary nanoclusters were prepared with different atomic ratios of Au:Co using pulsed-voltage electrodeposition at 20 kHz from electrolytes with varying concentrations of Au and Co cations. The electrocatalytic activities of the different catalysts deposited on rotating disk electrodes were evaluated for the oxygen reduction reaction (ORR) using voltammetry. The Au/CoOx binary electrocatalysts with less than 1.2% Co atoms were found to increase the ORR activity compared to those of either the pure Au or pure CoOx. As the Co content in the binary mixture was increased, a maximum in the Au electronegativity, as measured by X-ray photoelectron spectroscopy, was observed which corresponded to a maximum observed rate for oxygen reduction. The Au: Co atomic ratio at the maximum rate was approximately 80:1. The number of electrons transferred in the oxygen reduction decrease from four to two as the Co content increased, suggesting that the electroreduction pathway is altered by the presence of Co. (c) 2007 The Electrochemical Society.