Electrochemistry of Fuel Cell Electrodes. Surface Oxidation of Gold Electrodes

Abstract

The surface oxides formed on electropolished gold by potentiostatic anodization in the range 1.2-1. 8 v vs. Fr/H^in the same solution, hnve bacn studied by galvanostatic reduction at current densities between 10 and 100C^ta-/errir Molar perchlorate solutions of pH 0. 04 to 2. 1 were employed. The extent of oxide formation is determined by the potential of anodization, the charge increasing linearly with the potential of formation in the range of 1.4 to 1.8 v. Cathodic chronopotentiograins show that reduction of the oxide occurs at a definite potential which depends on the cathodic current density. Current-potential curves, constructed from the chronopotentiograms, TMlow a Tafel relation with a slope of 41 mV. The exchange current for okide reduction decreases with pH and with increasing potential of formation of the oxide. The electrochemical order of the reduction reaction\is -1. 65 with respect to pH. A mechanism for reduction is suggested in wtfiich it is assumed that the reduction of an intermediate (Au ) is the slo in the overall process.