Electrochemical Characterization of MnO2 Anodically Formed During the Zinc Electrowinning Process

Abstract

This work describes the different species formed over a lead-silver substrate after being applied an oxidation potential pulse in an electrolyte similar to that employed in the electro-recovery of zinc. At the beginning, a layer of PbSO4 is developed, followed by the formation of PbO2, which is catalyzed by the presence of Mn(II) in the electrolyte; after 5 minutes occurring this process, a layer of MnO2 is electrochemically formed over the PbO2. The manganese oxide catalyzes in major proportion the oxidation of other species of manganese to MnO4- than the oxygen evolution reaction. Furthermore, this manganese film shows resistive properties increasing the overpotential oxidation process.