Effects of polyaniline on electrochemical properties of composite inert anodes used in zinc electrowinning

In order to search for a suitable anode material used in zinc electrowinning in place of Pb-Ag alloy, Al/Pb-PANI (polyaniline)-WC (tungsten carbide) composite inert anodes were prepared on aluminum alloy substrate by double pulse electrodeposition (DPE) of PANI and WC particles with Pb2+ from an original plating bath. Thereafter, anodic polarization curves, cyclic voltammetry curves and Tafel polarization curves for the composite inert anodes obtained under different PANI concentrations in the original plating bath were measured, and the microstructural features were also investigated by scanning electron microscopy (SEM). The results show that Al/Pb-PANI-WC composite inert anode obtained under PANI concentration of 20 g/L in the original plating bath possesses uniform microstructures and composition distributions, higher electrocatalytic activity, better reversibility of electrode reaction and corrosion resistance in a synthetic zinc electrowinning electrolyte of 50 g/L Zn2+, 150 g/L H2SO4 at 35 °C. Compared with Pb-1%Ag alloy, the overpotential of oxygen evolutions for the composite inert anode are decreased by 185 mV and 166 mV, respectively, under 500 A/m2 and 1000 A/m2.