Electrochemical reactions on metal-matrix composite anodes for metal electrowinning

In this study, Pb-MnO₂ composite anodes were developed through single-action powder pressing. The effect of MnO₂ content of the composite anodes on the physical and electrochemical properties of the samples were investigated and compared with those of the pure pressed Pb and a commercial Pb-Sn-Ca electrowinning anode. Surface morphology of the fabricated samples was examined using scanning electron microscopy (SEM). Cyclic voltammetry and potentiodynamic polarization experiments were performed in 180 g/l sulphuric acid solution at 37 ± 0.5°C to study the surface reactions of the anodes and their performance in terms of oxygen evolution reaction (OER) rate and potential. The results indicated that the addition of MnO₂ improved the electrocatalytic activity of the lead anode for oxygen evolution. Oxidation of lead was also influenced by MnO₂ particles. The effects of manganese ions in the electrolyte on the electrochemical performance of the composite anodes were also studied. Results showed that manganese ions, depending on concentration, can have both promoting and suppressive effects on the OER on the composite anodes.