ELECTROCHEMISTRY OF FUEL CELL ELECTRODES. SURFACE OXIDATION OF GOLD ELECTRODES.

摘要

The surface oxides formed on electropolished gold by potentiostatic anodization in the range 1.2 - 1.8 v vs. H(+)/H2in the same solution,were studied by galvanostatic reduction at current densities between 10and 1000 *microemperes/sq cm. Molar perchlorate solutions of pH 0.04to 2.1were 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 1.4to 1.8 v. Cathodic chronopotentiograms 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,follow a Tafel relation with a slope of 41mV. The exchange current for oxide reduction decreases with pH and with increasing potential of formation of the oxide. The electrochemical order of the reduction reaction is -1.65with respect to pH. A mechanism for reduction is suggested in which it is assumed that the reduction of an intermediate (Au II) is the slow step in the overall process. (Author)