Controllable Preparation And Electrochemical Performance Of Titanium Dioxide Nanotube-modified Active Energy-saving Anodes

This paper proposes a novel energy-saving anode synthesis path for the high oxygen evolution overpotential and high energy consumption of lead-silver alloy anodes in the zinc hydrometallurgy industry.Using titanium as the substrate,firstly,TiO₂-NTs arrays with good conductivity were synthesized in situ by the"anodization-anneal modification-electrochemical reduction modification"technology.Then,PbO₂ coating doped with carbon nanotubes and manganese dioxide was prepared by composite electrodeposition technology.Finally,a novel Ti/TiO₂-NTs/PbO₂-CNTs-MnO₂ composite anode that can improve the current efficiency and reduce the energy consumption of zinc electrowinning was successfully prepared.Firstly,the regulation rule of"anodization-anneal modification-electrochemical reduction modification"technology on the morphology and phase of TiO₂-NTs and the modification of composite anode were studied.In anodization,the presence of H₂O in the system was necessary for the formation of TiO₂-NTs;the operating voltage increased,the tube diameter increased;with the increased of temperature,tube diameter and length increased;too much time could cause the top to collapse;additional anodization reduced the oxygen evolution overpotential.Annealing transformed the amorphous TiO₂-NTs into anatase at 450?.The electrochemical reduction partially reduced the tetravalent titanium,which enhanced the conductivity of the nanotubes,thereby reducing the overpotential.Finally,a uniformly arranged nanotube array with a tube diameter of?120 nm and a tube length of?8?m was prepared.In addition,the introduction of the TiO₂-NTs array eliminated the cracks in the PbO₂ coating,refined the crystal grains,increased the electrochemical specific surface area,reduced the charge transfer resistance,and enhanced the corrosion resistance and electrocatalytic activity of the composite material.Secondly,the influence of PbO₂ electrodeposition on the electrocatalytic activity of the composite anode was studied.Ti/TiO₂-NTs/PbO₂ prepared under optimal conditions(0.2 M Pb²⁺,p H 3,40?,20 m A/cm²,1h)exhibited good electrocatalytic activity and corrosion resistance.Single doping of CNTs had limited effect on enhancing electrocatalytic activity.When co-doped with MnO₂,the electrodeposition behavior of CNTs was changed.Ti/TiO₂-NTs/PbO₂-CNTs-MnO₂ prepared under 3 g/L MnO₂ and 0.7g/L CNTs showed the smallest charge transfer resistance,the largest specific surface area and the best electrocatalytic activity.The oxygen evolution overpotential(451 m V)was reduced by 511 m V compared with Pb-0.76 wt%Ag(150 g/L H₂SO₄,50 g/L Zn²⁺,50m A/cm²,35?).This is mainly attributed to the high electron mobility and large specific surface area of the nanotube array,promoting the electron transport at the interface;particle doping refines the PbO₂ grains and promotes the formation of three-dimensional structure on the coating surface.Finally,the performance of composite anodes in long-period zinc electrowinning was studied.Among them,Ti/TiO₂-NTs/PbO₂-CNTs-MnO₂ exhibited an optimal energy-saving effect.Compared with Pb-0.76 wt%Ag,the cell voltage was reduced by 0.38 V,the current efficiency was increased by 3.1%,the energy consumption was reduced by 456.220 k W·h/t,and the theoretical service life reached 2800 days.Therefore,Ti/TiO₂-NTs/PbO₂-CNTs-MnO₂ may be an ideal anode material for zinc electrowinning.