Study Of Electrocatalytic Reaction For The Electrode In Zinc Electrowinning System

Zinc electrowinnning process causes huge consumption of zinc hydrometallurgy industry.Reducing energy consumption is conducive to the environment.During electrowinning,oxygen evolution occurs at the anode,zinc and hydrogen evolution occurs at the cathode.Reduce the overpotential of electrode reaction,and lower the cell voltage of total reaction is a way to solve this problem.Electrocatalysis is an effective way to reduce the overpotential of electrode reaction,thus reducing the electrode potential and cut down the energy consumption.In this work,three kinds of carbon-based catalysts were prepared for the oxygen evolution reaction of zinc electrowinning,the physics properties of catalysts,and the electrocatalytic performance of the zinc electrodeposition process were studied.The electrochemical performance for zinc nuclearization and hydrogen evolution effects of organic/inorganic additives during the zinc electrowinning process were studied.The main conclusions are as follows:1.The preparation of Hierarchical-network carbon catalyst（HNC）and the electrocatalytic performance of zinc electrodeposition anode reaction was studied,the conclusions are as follows:A Hierarchical-network carbon（HNC）oxygen evolution catalyst with unique spatial structure was prepared by electrodeposition-high temperature carbonization method on conductive carbon paper（CP）matrix.The HNC has a good liquid dispersion ability,which can fully contact with the electrolyte and provide abundant active sites,showing good catalytic activity for oxygen evolution.It shows excellent performance for OER in 50 g·L^-1 Zn²⁺+150 g·L^-1 H₂SO₄ solution,with an overpotential of 517 m V(@10 m A·cm^-2),a Tafel slope with 46 m V·dec^-1,and Cdl with 43.30 m F·cm^-2.Besides,there are no side reaction occurs,which can effectively avoid anode slime.In addition,during the zinc electrowinning simulation experiment,the cell voltage of HNC is 2.86 V in a short time,which is 8.6%lower than that of pure Pb anode 3.13 V.2.The preparation of self-supported carbon-based transition metal catalyst and the electrocatalytic performance of zinc electrodeposition anode reaction were studied,the conclusions are as follows:The Ni/CP and Fe O/CP composite catalysts were successfully prepared by one-step electrodeposition method,which was coated by nanometer transition metal/oxide Ni or Fe O on CP,exhibited remarkable mechanical properties and OER activity.The Ni/CP and Fe O/CP catalysts have the higher electrical double-layer capacity（Cdl）of which are 88.90 and 103.82 m F·cm^-2,respectively.Fe O/CP shows the best OER ability.In the zinc electrowinning simulation experiment,Ni/CP and Fe O/CP catalysts have a lower cell voltage of 2.80 and 2.82 V,respectively,which were significantly lower than that of pure Pb electrode.The cell voltage of the Fe O/CP electrode was steady than Ni/CP.3.The influences for different kinds of additives in zinc electrowinning system were studied,the conclusions are as follows:The additive can lower the overpotential of cathode reaction,reduce the impedance of the system,and optimize the surface morphology of cathode products.In the zinc electrowinning simulation experiment,the cell voltage from high to low is SDS>EDTA>Blank>Sr CO3>HA,the current efficiency from high to low is EDTA>Blank>SDS>HA>Sr CO3.HA additive shows an excellent performance in reducing the cell voltage,which was only 2.92 V,for about0.15 V lower than that of the group without additives.It has good application potential.