Anodic Process on Gold in the KF–AlF₃–Al₂O₃ Melt

Abstract—Under the conditions of resource saving and decreasing carbon footprint, the development of oxygen-releasing anodes for manufacturing technologies of important metals and alloys by the electrolysis of molten salts seems to be an urgent task. Data on the kinetics and mechanism of the anodic process on a material that is not prone to oxidation are needed to determine the degree of “inertness” of a particular anode material. In this connection, the anodic process on gold in the KF–AlF₃–Al₂O₃ melt for electrolytic aluminum production is studied by cyclic voltammetry (CV) and square-wave voltammetry. The influence of temperature (715 and 775°C) of the melt, Al₂O₃ content in the melt (from 0.1 to saturation), and polarization rate (0.05–1 V/s) on the kinetics and some features of the mechanism of the studied process is determined. An oxygen release on gold without dissolution of the substrate is assumed to take place in the overvoltage range from 0 to 0.8 V. The process is shown to consist of 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.