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

Abstract

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.