Electrochemical engineering of anodic oxygen evolution in molten oxides

Molten oxide electrolysis (MOE) is a metal extraction process that exhibits an exceptionally high productivity in comparison with other electrowinning techniques. Furthermore, MOE has the ability to generate oxygen as an environmentally benign byproduct, which is a key asset to improve metal extraction sustainability. From an electrochemical engineering standpoint, the high concentration of metal cations dissolved in the electrolyte justifies cathode current densities above 10,000 A m−2. At the anode, the available data suggest a mechanism of oxidation of the free oxide anions which concentration in oxide melts is reported to be limited. In this context, the application of available mass-transfer correlations for the anodic oxygen evolution suggests a key role of convection induced by gas bubbles evolution.