In situ synthesis of an Al and V co-doped TiO ₂ NTA interlayer-enhanced PbO ₂ composite for efficient zinc electrowinning

The high overpotential of the oxygen evolution reaction (OER) and the strong corrosion of the anode are the main problems currently faced by the zinc hydrometallurgical process. This study achieved the successful in situ synthesis of titanium dioxide nanotubes doped by Al and V on a TC4 alloy. Subsequently, a composite electrode, TC4/AVTN-7/PbO₂-ZrO₂-Co₃O₄, was prepared utilizing composite electrodeposition. An investigation was conducted on the phase composition, surface morphology, electronic structure, and electrochemical performance of the composite electrode. The results indicate that Al and V co-doped TiO₂ nanotube arrays (NTAs) maintain their intact tubular morphology. The doping of Al and V reduced the band gap width of TiO₂ from 3.13 eV to 2.84 eV, making it easier for valence band electrons to transition to the conduction band, forming hole-electron pairs, and effectively enhancing the conductivity of the intermediate layer. The TC4/AVTN-7/PbO₂-ZrO₂-Co₃O₄ showed an overpotential (η) of 660 mV at 50 mA cm^-2 in an electrolyte with 50 g L^-1 Zn²⁺ and 150 g L^-1 H₂SO₄. Compared to TC4/AVTN-7/PbO₂, its η value is decreased by 243.32 mV. At a high current density of 2 A cm^-2, the accelerated corrosion life reached 39 hours in 1.5 M H₂SO₄ medium. In long-term zinc electrowinning simulation tests, TC4/AVTN-7/PbO₂-ZrO₂-Co₃O₄ exhibited excellent stability. Compared with traditional lead-silver alloy anodes, the cell voltage and power consumption of TC4/AVTN-7/PbO₂-ZrO₂-Co₃O₄ decreased to 2.82 V and 2649.46 kWh t^-1 Zn^-1, respectively, demonstrating significant energy-saving benefits.