Structural Regulation And Hydrogen Evolution Performance In Alkaline Electrolytic Water Of MoSe₂ Based Catalyst

The technology of hydrogen production by alkaline electrolysis of water is safe and reliable.The use of catalysts can effectively reduce the energy barrier of the cathodic hydrogen evolution reaction and improve the reaction rate.In meet the requirements of efficient hydrogen production in actual industrial production,it is necessary to develop catalysts with low overpotential and low cost at high current density.MoSe₂ nanomaterials have high theoretical hydrogen evolution catalytic activity and△G_H*>0,which is conducive to hydrogen desorption at high current density.However,there are some problems such as a high energy barrier of the water dissociation reaction in an alkaline solution,few active sites,and poor conductivity.Therefore,this thesis took MoSe₂ as the research object and optimized the composition and structure of the material to improve△G_H*,the number of active sites,and the electrical conductivity.The mechanism of the influence of Ni modification,heterostructure construction,and carbon composite modification on the performance of hydrogen evolution was elucidated,and a MoSe₂-based catalyst with low overpotential under high current density was obtained.To solve the problem of the high energy barrier of water dissociation reaction of MoSe₂ in the alkaline electrolytic water hydrogen evolution reaction,a Ni nanocluster-modified MoSe₂ catalyst was designed and prepared.There is a synergistic effect between Ni and MoSe₂.Ni enhances the adsorption ability of MoSe₂ to OH^-,improves the dissociation rate of H₂O to H⁺,and increases the concentration of H⁺on the catalyst surface,thereby improving the H⁺conversion efficiency.Ni modification effectively reduced the additional energy barrier of water dissociation reaction and increased the catalytic activity of Ni-MoSe₂.When the nominal content of Ni is 9 at.%,the overpotential of Ni-MoSe₂ at 10m A/cm² is 186 mV,which is 198 mV lower than that of MoSe₂.In this paper,the strategy of constructing a heterostructure catalyst and adjusting the heterostructure interface to increase the number of active sites was proposed.Using Ni Mo O₄ as the precursor,a hollow rod-like Ni_xSe_y-MoSe₂heterostructure catalyst with high heterostructure interface density was prepared by hydrothermal selenization using self-templating method.After the formation of the heterostructure,the band structure of the catalyst is changed,the center of the d band is moved up,and the adsorption of H^*is enhanced,which is conducive to the occurrence of the hydrogen evolution catalytic reaction.The improved catalytic performance of Ni_xSe_y-MoSe₂ with high interfacial density was attributed to the increased number of active sites due to the dense heterogeneous interface and the hollow rod-like structure.The heterostructured catalyst with a phase composition of NiSe and MoSe₂ showed the best hydrogen evolution activity with an overpotential of 151 mV at 10 m A/cm².To improve the conductivity of the catalyst,the NiSe-MoSe₂ heterostructure was carbon complexed and the degree of crystallization was regulated.Amorphous carbon was generated in situ during the formation of Ni Mo O₄ by urea pyrolysis,and the morphology of the oxide precursor was adjusted at the same time to prepare hollow spherical Ni Mo O₄/C.Then,the Kirkendall effect in hydrothermal selenization was used to further expand the degree of cavitation,and a high heterogeneous interface density NiSe-MoSe₂/C hollow spherical catalyst was constructed.After carbon composite,the conductivity of NiSe-MoSe₂/C was enhanced,and the charge transfer rate in the catalyst was increased.The hollow spherical geometry increases the specific surface area,the number of active sites,and the catalytic reaction rate of hydrogen evolution.By regulating the carbon content of NiSe-MoSe₂/C,the charge transfer rate of NiSe-MoSe₂/C can be further increased,the conductivity can be enhanced,and the catalytic activity can be improved.In addition,the crystallization degree of NiSe-MoSe₂/C was improved by optimizing the hydrothermal reaction time under the hydrothermal process of complete selenization of oxide precursors.While retaining more active sites formed by the amorphous phase and defects,the charge transfer resistance of NiSe-MoSe₂/C was reduced to improve the catalytic performance of NiSe-MoSe₂/C at high current density.NiSe-MoSe₂/C had the best catalytic performance for hydrogen evolution when the added content of urea was0.6 g and the hydrothermal reaction time was 18 h,and it had a lower overpotential at both small and large current densities.The overpotentials at 10 m A/cm² and400 m A/cm² were 138 mV,and 365 mV,respectively.The overpotential was 534mV at 1000 m A/cm²,which was superior to that of the commercial Pt/C catalyst（555 mV）.