Gas Diffusion Electrode With The Low Loading Pt/N-C Catalysts And Its Application On Zinc Electrowinning

Industrial zinc hydrometallurgy generally lead-silver alloy is used as anode,however,oxygen evolution reaction occurred at the anode,so acid mist will be generated.And it will lead to a higher cell voltage,which wastes a lot of electrical energy.Therefore,reducing the higher energy consumption of zinc electro winning is an urgent problem to be solved.Compared with the traditional lead-silver alloy anode the anodic reaction changes from 2OH--2e-=H2O+0.5O2 to H2-2e-=2H+,when using hydrogen diffusion anode for zinc electrowinning.In theory the cell voltage can be reduced about 1.23 V,besides,there is no oxygen evolution overpotential,and reduced the acid mist.In this thesis,the low-loading Pt/N-C catalysts were prepared by impregnation reduction method.Firstly,sodium citrate and urea were mixed in a ratio of 10:1,and then under the Ar annealed at 800? for 2 h,to obtained nitrogen-doped carbon support.Take 100 mg of nitrogen-doped carbon support,add deionized water make them uniformly dispersed.Then add 0.1 M H2PtCl6 aqueous solution mixed and stir for 10 h,dry by rotary evaporation.Last under Ar annealed at 800? for 45 min,obtained the low-loading Pt/N-C catalysts.And the electrochemical test shows that under the same overpotential,the mass activity of the low-loading Pt/N-C catalyst is about 32 times that of Pt/C.The limiting current density is comparable to Pt/C,but the half-wave potential is lower 9 mV than commercial Pt/C.In this paper,we simplify the preparation process of the traditional gas diffusion electrodes.We use carbon cloth as substrate and diffusion layer,the low-loading Pt/N-C catalysts as catalytic layer.It can be seen that platinum content is only 0.19 mgpt/cm2 of the hydrogen diffusion anode.And the influence of different current density,electrodes distance,zinc sulfate concentration,additive content,sulfuric acid concentration and different time was explored of zinc electrowinning.The research shows that under the best process parameters,the cell voltage is about 1.20 V when using hydrogen diffusion anode to zinc electrowinning.The cell voltage is 33.3%of industrial zinc electro winning,and the energy consumption is 1235.1 kW·h/t,which is 38.7%of industrial zinc electrowinning.