PbO₂ modified with TiO₂-NTs composite materials with enhanced OER electrocatalytic activity for Zn electrowinning

The high oxygen evolution overpotential of the Pb-Ag anode is one of the main reasons for the high energy consumption in Zn electrowinning. PbO₂, owing to its high conductivity, good corrosion resistance and low cost, is widely used as an excellent coating material. In present research, a novel composite Ti/TiO₂-NTs/PbO₂ material was synthesized through a facile anodization, annealing, electrochemical reduction and galvanostatic deposition. The surface morphology, internal structure and the mechanisms of TiO₂-NTs enhancing electrochemical performance were discussed. The results show that the self-organized high aspect ratio TiO₂-NTs with diameter of ∼120 nm and length of ∼8 μm were obtained on Ti substrate. The Ti/TiO₂-NTs/PbO₂ composite material exhibits excellent oxygen evolution performance and good stability in Zn electrowinning simulation solution (50 g L^-1 Zn²⁺, 150 g L^-1 H₂SO₄) at 35 °C. Its oxygen evolution overpotential is only 630 mV under current density 50 mA cm^-2, which is 332 m lower than that of Pb-0.76 wt% Ag (η = 962 mV) and only increases 22 mV after 5000 cycles of CV scanning. Its outstanding electrochemical performance is mainly ascribed to the introduction of TiO₂-NTs in Pb(CH₃COO)₂ media since it refines the crystal grains, increases the electrochemical surface area, greatly reduces the charge transfer resistance (25.4 Ω cm² to 2.337 Ω cm²) and enhances corrosion resistance. Therefore, the Ti/TiO₂-NTs/PbO₂ material prepared in Pb(CH₃COO)₂ medium may be an ideal anode for Zn electrowinning.