Effects Of Morphology And Content Of Platinum Catalyst On Electrowinning Performances Of Zinc By Gas Diffusion Electrode

Hydrometallurgy,as the current main way of zinc refining,produces 80%metal zinc of the total zinc production.In the traditional electrowinning process of zinc,the oxygen evolution reaction on the anode of lead alloy leads to a high reaction potential,which causes large energy consumption in the whole process.The hydrogen diffusion anode(HDA)can be used instead of the traditional lead anode for zinc electrowinning.By changing the reaction on the anode,the cell voltage can be reduced to save energy.This thesis focuses on the platinum catalyst for the catalysis of the hydrogen oxidation reaction(HOR)on HDA,The surface morphology of platinum catalysts is designed and their doping content is regulated to study their influence on electrowinning of zinc.In addition,the preparation process of HDA was also explored in this thesis.In this thesis,using chloroplatinic acid,ethylene glycol,dimethylformamide and commercial carbon black as materials,using hydrothermal prepared platinum catalyst.By adjusting the proportion of each component to induce the surface structure of platinum catalyst,and the platinum nanoparticles with octahedral morphology and tetrahedral morphology were constructed.Then,we characterized and studied the relationship between the morphology,content and catalytic performance of these catalysts.Using carbon cloth,platinum catalyst,commercial carbon black,isopropyl alcohol and polytetrafluoroethylene as materials,the gas diffusion electrode were prepared and applied to electrowinning of zinc.Then we studied the electrochemical parameters related to the electrowinning process,which are cell voltage,current efficiency and direct current unit consumption.The main research results are as follows:(1)The platinum nanoparticle catalysts with tetrahedral morphology and octahedral morphology are prepared.And tetrahedral platinum nanoparticle catalysts have good application performance in HOR,with limiting current density reaching 3.28 m A/cm~2,reaction overpotential of 10 m V,and mass activity of 42.9 m A/mg at 40 m V superpotential.After 5,000 potential cycles,the limiting current density of platinum tetrahedral catalyst can still retain 86%of the original state,and the mass activity of tetrahedral platinum catalyst retains about 60%after carbon monoxide poisoning.Compared with commercial platinum catalyst,it has obvious advantages.(2)Carbon supported platinum catalysts with different doping content were prepared.After studying the electrochemical performance of HOR on these catalysts,we were found that the limiting current density of the platinum catalyst prepared with 5%platinum mass fraction is comparable to that of the commercial platinum carbon catalyst prepared with 20%platinum mass fraction,indicating that the catalyst prepared in this thesis can reduce the amount of platinum and the reaction cost on the premise of ensuring the catalytic performance of HOR.(3)Hydrogen diffusion anodes with different catalyst morphology and content were prepared by coating,cold pressing,sintering and hot pressing for electrowinning of zinc.The optimized parameters show that the electrode has the highest forming performance and economic benefit when the catalyst doping fraction on the electrode is 5%.When the electrode prepared by tetrahedral platinum catalyst is used for electrowinning of zinc,the cell voltage is only 1.19V,the current efficiency is 89%,and the direct current unit consumption is 1180 k Wh/t,which is better than the electrode prepared by commercial platinum carbon catalyst.