Study On Ni-based Hydrogen Electrode Based On Adsorption Free Energy Optimization

Today,the world’s energy structure mainly uses fossil energy.However,CO₂,CO,and PM2.5 generated during the use of fossil energy will endanger human health and cause environmental pollution.In this regard,the hydrogen energy economy provides a potential energy alternative in which hydrogen is produced by electrolysis of water and finally oxidized to form water.In the hydrogen economy,hydrogen evolution reaction（HER）and hydrogen oxidation reaction（HOR）are the two most critical parts.At present,platinum is the most commonly used electrocatalyst for HER and HOR,but the high cost of platinum group metals hinders the commercial development of water electrolysis and hydrogen fuel cells.With the development of alkaline anion exchange membranes and basic non-precious metal oxygen reduction reaction（ORR）/oxygen evolution reaction（OER）catalysts,the cost of hydrogen energy economy can be effectively reduced by using non-noble metal materials for water electrolysis and alkaline anion exchange membrane fuel cell in alkaline environment.Therefore,in order to realize the beautiful vision of hydrogen economy and reduce the cost of electrolyzed water and hydrogen fuel cells,we hope to develop non-precious metal materials with similar properties to platinum group metals.Nickel has high crustal content and low price,and a large number of studies have pointed out that nickel has the potential for HER/HOR development.Based on the two advantages of low cost and high activity,nickel-based materials were selected to optimize HER/HOR activity.Hydrogen adsorption energy and hydroxide adsorption energy are key descriptors of hydrogen electroactivity.And electrocatalysts with high HER/HOR activity should possess suitable hydrogen and hydroxide adsorption energies.Based on these two descriptors,this paper designs Ni-based hydrogen electrodes,optimizes HER/HOR activity,and further explores electrochemical activation,so as to reduce the cost of alkaline water electrolysis and hydrogen fuel cells,and facilitate the realization of hydrogen energy economy.The specific research work is as follows:1.Combining metallic Ni with excellent hydrogen adsorption energy and metallic W with excellent hydroxide adsorption energy,Ni/W bimetallic electrocatalysts were synthesized by a two-step method.Ni can provide hydrogen adsorption sites,while W can provide hydroxide adsorption sites,forming water desorption at the junction of the two,so the synthesized Ni/W bimetallic electrocatalyst can achieve excellent HER/HOR activity.2.In order to optimize the hydrogen electrical activity of Ni sites,the formation of MoO₂/Ni heterostructure can reduce the electron density of Ni sites and realize the simultaneous optimization of hydrogen adsorption energy and hydroxide adsorption energy.In the experiment,MoO₂/Ni nanosheets were synthesized,and it was proved that the morphology of the materials could be controlled by adjusting the amount of ethanol added,and the HER and HOR activities of the designed materials were compared and analyzed.3.In order to improve the stability of the catalyst,a doping method was chosen,and Ni was doped into the stable compound WO_x.Ni doping can cause the reconfiguration of the d-band electrons of W,and optimize the energies of hydrogen adsorption and hydroxide adsorption at the W site,thereby enhancing the HER performance.The effect of nickel doping amount on hydrogen evolution activity was investigated by synthesizing materials with different nickel doping amounts,and the activity for hydrogen production from alkaline seawater was explored.4.Ni-doped WOx is easily oxidized by electrochemical oxidation,resulting in unmeasured HOR activity.We focus on the electrochemical test process and the materials after electrochemical oxidation.It is found that electrochemical activation can enhance the HER/HOR activity of Ni-WO_x.The morphology and structure of the materials before and after electrochemical activation were compared and analyzed by characterization methods,and the reasons for the improvement of HER/HOR activity were analyzed.