Preparation And Electrocatalytic Performance Of Vanadium Compound Based Composites For Hydrogen Production

In the new century,The electrolysis of aquatic hydrogen is considered as one of the important technologies to solve the energy crisis by hydrogen energy because of its low cost and the clean materials of reactants and products.However,the reaction rate of hydroelectrolysis is slow in general,which limits its application in commercial production.In order to improve the rate of hydrogen evolution,it is very important to select suitable electrocatalytic catalysts for hydrogen production.However,the catalysts with better performance of electrocatalytic hydrogen production are mostly noble metals or transition metal compounds,which have high cost of raw materials and small reserves.Therefore,it is necessary to develop electrocatalytic catalysts with better electrochemical catalytic performance,simpler preparation process,low cost and no pollution.Vanadium,as an element with more content in nature,vanadium compounds are widely used in People’s Daily production and life.Among them,V₂O₃and VC have certain electrocatalytic hydrogen production performance,but their catalytic performance still needs to be further improved if they are to be used in the actual commercial production field.In this paper,we study the preparation of Ni-V₂O₃and C-VC composites and the effect of preparation conditions on the morphology and catalytic performance of the composites.The main research work carried out and the main research results obtained are:（1）The preparation technology and formation mechanism of Ni-V₂O₃and C-VC composites were studied.Using electrochemical molten salt method,applying electrolytic voltage to molten Na VO₃at high temperature of 850^oC,VO₃^-was electronically reduced to V₂O₃.When the cathode material for electrolysis is nickel foam,V₂O₃is deposited on the nickel foam to form a rich Ni/V₂O₃interface,forming composite Ni-V₂O₃.When the cathode material for electrolysis is carbon cloth,V₂O₃is reduced to VC at high temperature,and VC is deposited on the carbon cloth to form C-VC composite material.（2）The influence of electrolysis conditions on the morphology and catalytic performance of composites was studied.It is found that the electrolysis voltage has a greater effect on the composite than the electrolysis time.Under acidic conditions,When the electrolysis voltage was 2.8 V for 5 min,V₂O₃formed on the surface of nickel foam showed nanoribbon array structure with large specific surface area and many active sites,and the composite Ni-V₂O₃formed had the best catalytic performance for hydrogen production.When the current density of polarization curve reaches 10 m A cm^-2,the overpotential only needs 159 m V.When the electrolysis voltage is 2.2V for 30 min,VC formed on the surface of carbon cloth is arranged as interconnected nanowires,forming an efficient electron transfer network with large specific surface area and fully exposed active sites.C-VC composite has the best catalytic performance of hydrogen production,and the current density of polarization curve reaches 10 m A cm^-2.The overpotential is only 141 m V.（3）The catalytic hydrogen production performance of the prepared composite,the substrate,the substrate loaded with Pt/C and the substrate loaded with precursors was compared and studied.The results show that the composite between materials produces an interface between different materials,and this interface effectively affects the performance of the composite.The electrochemical catalytic performance of the composite material for HER showed that the charge transfer resistance of nickel foam decreases after deposition of V₂O₃,the specific surface area of the material increases,and the active sites are fully exposed.The Ni/V₂O₃interface constructed by nickel foam and V₂O₃can promote the electron transfer between the substrate and the reaction intermediates.There is a synergistic effect between nickel foam and V₂O₃on electrocatalytic hydrogen production.Similarly,in the C-VC synthesis process,the charge transfer resistance of carbon cloth decreases after deposition of VC,the specific surface area of the material increases,and the active site is fully exposed.The catalytic performance of C-VC is far better than that of carbon cloth and VC.The Tafel slope of C-VC is only 60.04 m V Dec^-1.It shows that there is synergistic effect between carbon cloth and VC in electrocatalytic hydrogen production.