Effects of tungsten carbide on electrochemical properties and microstructural features of Al/Pb-PANI-WC composite inert anodes used in zinc electrowinning

In order to search for a suitable anode material in place of Pb–Ag alloy in zinc electrowinning, Al/Pb-PANI(polyaniline)-WC(tungsten carbide) composite inert anodes on aluminum substrates were prepared by double pulse electrodeposition (DPE) of WC and PANI particles with Pb2+ from an original plating bath, in which solid particles were suspended by mechanical stirring. Thereafter, the anodic polarization curves, cyclic voltammetry curves and tafel polarization curves for the composite inert anodes obtained under different WC concentrations in the original plating bath, were measured in a synthetic zinc electrowinning electrolyte of 50 g·L− 1 Zn2+, 150 g·L− 1 H2SO4 and 35 °C, and the microstructural features were also observed by scanning electron microscope (SEM). The results show that the co-deposition of WC and PANI particles with Pb2+ in the original plating bath, changes the electrocrystallization morphologies for matrix metal Pb on aluminum substrates. Al/Pb-PANI-WC composite inert anode obtained under WC concentration of 30 g·L− 1 and PANI concentration of 20 g·L− 1 in the original plating bath, possesses uniform surface and cross sectional microstructures, higher electrocatalytic activity, lower overpotential of oxygen evolution, better reversibility of electrode reaction, better corrosion resistance and longer service times in a synthetic zinc electrowinning electrolyte of 50 g·L− 1 Zn2+, 150 g·L− 1 H2SO4 and 35 °C.

► Al/Pb-PANI-WC composite inert anode may be a suitable anode material in zinc electrowinning.
► The co-deposition of solid particles changes the electrocrystallization morphologies of Pb.
► The anode possesses higher electrocatalytic activity and better reversibility of electrode reaction.
► The anode possesses lower overpotentials of oxygen evolution and longer service lifetimes.