Oxygen evolution behaviours of novel porous MnxSiy electrodes for metal electrowinning

In this study, three types of novel porous MnxSiy oxygen electrodes for metal electrowinning were prepared by elemental powders reactive synthesis. The electrocatalytic activity and corrosion resistance of the porous MnxSiy electrodes were evaluated. The results demonstrated that the electrodes with lower silicon content presented lower potential during a 24-h polarization period and that the corrosion resistance of MnxSiy electrodes was enhanced as the Si content increased. Among these prepared oxygen electrodes, the porous Mn5Si3 electrode exhibited the highest catalytic activity towards oxygen evolution reaction (OER) in 1.63 mol l(-1) sulfuric acid solutions. The influence of the electrode active surface on electrocatalytic activity was also studied, and the results showed that large active surface greatly promoted the electrocatalytic performance of the electrodes. The porous MnxSiy electrodes were also tested in conditions which simulate industrial zinc electrowinning and compared to conventional Pb and Pb-Ag (0.8 wt%) anodes. The current efficiency of porous Mn5Si3 electrode reached 85.7%, which was comparable to that of Pb and Pb-Ag (0.8 wt%) anodes. Moreover, the zinc cathode exhibited much lower impurity content. Besides, the addition of Mn2+ ions was also found to result in blockage of pores and increase of potential.