Anode Process on Gold in KF-AlF3-Al2O3 Melt

Currently, the development of oxygen-evolving anodes for eco-friendly technologies to produce important metals and alloys by electrolysis of molten salts seems to be an urgent task. To determine the degree of “inertness” of a particular anode material, data on the kinetics and mechanism of the anode process on an ideal material not subject to oxidation are required. In this connection, the anode process on gold in the low-temperature KF-AlF3-Al2O3 melt for electrolytic aluminum production was investigated in this work by cyclic and square-wave voltammetry methods. The influence of temperature (715 and 775°C) of the melt, the content of Al2O3 in it (from 0.1 to saturation), as well as the polarization rate (0.05–1 V s−1) on the kinetics and some features of the mechanism of the investigated process was determined. An assumption is made that oxygen release on gold without dissolution of the substrate takes place in the region of overvoltages from 0 to 0.8 V. It is shown that the process includes the stages of electrochemical adsorption and desorption of the intermediate product, the first of which is limited by the diffusion of electroactive anions to the anode.