Preparation And Stability Of Vanadium-based Composite Porous Hydrogen Evolution Cathode

Hydrogen（H₂）has garnered significant attention due to its high energy density,environmental friendliness,and abundant elemental availability.Electrolytic water is an exceptionally efficient hydrogen production technology that enables the direct production of high-purity hydrogen.Utilizing intermittent energy sources,such as solar and wind energy,to generate electricity and subsequently using electrolytic water to produce hydrogen that can be stored and transported is regarded as an effective solution to current energy scarcity and environmental pollution problems.However,the development of hydrogen production technology via water electrolysis is currently limited by the high cost of electrode materials,high hydrogen evolution overpotential,poor resistance to intermittent power supply,and inadequate stability.This paper primarily focuses on two key aspects:improving anti-discontinuous power supply capability and reducing hydrogen evolution overpotential.The authors have developed a hydrogen evolution cathode material with good catalytic activity and stability by employing a matrix material possessing a certain hydrogen storage capacity in combination with a high catalytic activity coating.This paper presents the preparation of vanadium-based porous alloy matrix materials using vanadium,titanium,and nickel metal powders through powder solid-phase sintering.The surface of the material was electrodeposited with Ni-Cu-Mo ternary alloy coatings to create vanadium-based porous composite electrodes with high hydrogen evolution activity.The electrocatalytic hydrogen evolution performance and stability of the composite electrode material were studied by a series of physical and chemical detection methods.The specific research results are as follows:（1）It is found that the surface morphology,porosity and catalytic capacity of the sintered matrix are greatly affected by the forming and sintering systems.The experimental results show that the optimum process parameters of sintered matrix materials are as follows:30%addition of ammonium bicarbonate as the pore-forming agent,molding pressure of 130 MPa,sintering temperature of 950°C,and a holding time of 4 hours.The resulting vanadium-based porous alloy matrix exhibits rich and uniform pores,with a porosity of 50.71%,an open porosity of 31.76%,a hydrogen evolution overpotential of 268 m V,Charge transfer resistance 92.7Ω,and an electrochemical active surface area（ECSA）of 5.69 cm².Additionally,the hydrogen evolution overpotential is lower than that of iron sheet electrode and copper sheet electrode under the same conditions.（2）Combined with first-principles calculations,the role of different coatings in hydrogen evolution catalysis is explained from the perspective of hydrogen adsorption free energy and binding energy.The advantages of Ni-Cu-Mo ternary coating in hydrogen adsorption and desorption compared with Ni-Cu and Ni-Mo binary coatings were clarified,and why Ni-Cu-Mo ternary coating was selected was systematically explained.Combined with the electrochemical study of the solution system,the complexation reaction of three metal ions in the system was mastered,and the general reaction process in the electrodeposition process was speculated.（3）According to the electrodeposition experiment,the optimum technological parameters for preparing vanad-based composite electrode by electrodeposition are as follows:deposition time 45min,concentration of trisodium citrate 0.25mol/L,current density 100 m A/cm²,deposition temperature 35℃and p H value 8.The overall surface of the electrode is uniform and flat.The three metals of nickel,copper and molybdenum are evenly distributed on the surface,with the mass percentage of 45.13%,44.48%and10.39%,respectively.The nickel and molybdenum are in the oxidized state,and the copper exists in the form of elemental.（4）Through a series of electrochemical tests,the hydrogen evolution overpotential of the Vad-based composite porous hydrogen evolution cathode material is 93 m V,which is higher than that of the Ni-Cu binary electrode.In the AC impedance tests at different potentials,the Rct values are 23.85,7.19,2.57Ω,respectively,and the ECSA of the electrochemical active surface area is 8.26 cm2.It can be seen that the composite electrode has excellent catalytic activity of hydrogen evolution.After 100h electrolysis,the catalytic activity of hydrogen evolution electrode changes slightly,which proves that the electrode has good corrosion resistance and intermittent power supply resistance.