Electrochemical behavior of rolled Pb–0.8%Ag anodes in an acidic zinc sulfate electrolyte solution containing Cl− ions

Abstract

In this study, the oxygen evolution kinetics and oxide layer properties of Pb–0.8%Ag rolled-alloy anodes were investigated during 15d of galvanostatic electrolysis in an acidic zinc sulfate electrolyte solution containing 600mg·L−1 Cl− ions. Cyclic voltammetry, quasistationary polarization, and electrochemical impedance spectroscopy were used to investigate the anode process. The microscopic morphology and phase composition of the anodic oxide layers were observed by scanning electron microscopy and X-ray diffraction, respectively. The observable variations in the electrocatalytic activity and reaction kinetics of the anodes during electrolysis indicate the formation and stabilization of the anodic oxide layer. With prolonged electrolysis, the oxygen evolution overpotential in the anodes mainly exhibited a decreasing trend, which is contrary to the trend of the electrode surface exchange current density. This depolarization may have been caused by the increasing roughness of the anodic surface and the catalytic effects of α-PbO2 and β-PbO2. As electrolysis continued, the cathodic peak (α-PbO2→PbSO4) mainly showed an increasing trend and gradually moved toward the negative direction. After 15days of electrolysis, the oxide layers exhibited a severely corrosive microstructure with plenty of cavities and etch pits. The uniform, well-defined crystal grains and regularity were not appeared. The phase composition of the anodic oxide layer was formed after 6d of electrolysis. α-PbO2 proved to be the main peak and showed preferential growth orientations along the (111) planes of the anodic oxide layer.