Understanding Anode Overpotential

Abstract

In aluminium electrolysis cells the anodic process is associated with a substantial overpotential. Industrial carbon anodes are produced from a blend of coke materials, but the effect of coke type on anodic overpotential has not been well studied. In this work, lab-scale anodes were fabricated from single cokes and electrochemical methods were subsequently used to determine the overpotential trend of the anode materials. Attempts were then made to explain these trends in terms of both the physical and chemical characteristics of the baked anodes themselves and their raw materials. Routine coke and anode characterisation methods were used to measure properties such as impurity concentrations and reactivity (to air and CO2 ), while non-routine characterisation methods were applied to study other surface and structural properties. It was found that the overpotential trend of the anodes correlated well with many of the properties studied, and explanations for these observed correlations are suggested. These findings offer exciting possibilities for reducing the energy demand of the anodic process.