Study On Modified Preparation And Electrocatalytic Performance Of MoS₂/NiSe₂ Nano-Heterostructure

The development and use of clean energy is an important guarantee for the sustainable development of human society.The preparation of clean energy H₂by electrolyzed water is one of the best ways to produce large-scale hydrogen in the future,but the electrocatalysts currently used commercially are generally noble metal catalysts such as Pt,Ir,Ru,etc.,which are costly and difficult to promote on a large scale.Therefore,the development of non-precious metal electrocatalysts is of great significance for large-scale hydrogen production from water electrolysis.Nickel diselenide（NiSe₂）and molybdenum disulfide（MoS₂）have attracted attention due to their abundant reserves,low price,easy availability,and good catalytic performance.This thesis takes NiSe₂and MoS₂as the research objects,explores the controllable preparation methods of nano-heterostructure electrocatalysts,at the same time adjusts the heterostructure to optimize the performance of oxygen evolution and hydrogen evolution,and studies the mechanism of improving catalytic performance.The main research contents are as follows:（1）The MoS₂/NiSe₂nano heterostructure catalyst was prepared by a simple two-step hydrothermal method.By adjusting the ratio of nickel and molybdenum atoms,the synergy in the heterostructure of MoS₂/NiSe₂is adjusted,the prepared MoS2/NiSe2-0.6 catalyst with an atomic ratio of nickel to molybdenum of 1:1 has better electrocatalytic performance in alkaline solution.The overpotential of the sample is only 299 m V at a current density of 20 m A cm^-2in oxygen evolution reaction（OER）,and 141 m V at a current density of 10 m A cm^-2in hydrogen evolution reaction（HER）.At the same time,it has excellent durability.（2）In order to improve the self-aggregation and poor conductivity of MoS₂/NiSe₂heterostructure,we choose graphene oxide（GO）as the substrate,and construct MoS₂/NiSe₂heterostructure on r GO by hydrothermal method.And a series of MoS₂/NiSe₂/r GO composite materials were successfully prepared.MoS₂/NiSe₂/r GO combines the good conductivity and dispersion of r GO substrate and the synergistic effect of MoS₂/NiSe₂heterostructure,which further optimizes the electronic structure of NiSe₂and MoS₂,showing a better performance than MoS₂/NiSe₂.In particular,the MoS₂/NiSe₂/r GO-0.6 sample has an overpotential as low as 277 m V at a current density of 20 m A cm^-2in OER,and the Tafel slope is only107 m V dec^-1.At the same time,the overpotential is 127 m V at a current density of10 m A cm^-2in HER,and the Tafel slope is 59 m V dec^-1.Finally,the dual-functional catalyst is used as a cathode and an anode.It only needs a low voltage of 1.52 V to provide a current density of 10 m A cm^-2in an alkaline solution and has good durability.（3）In order to explore the reasons why the nickel-molybdenum system catalyst has high-efficiency catalytic performance,a NiSe₂/MoS₂heterostructure was constructed on carbon cloth by combining hydrothermal,electrodeposition and solvothermal methods.This composite material exhibits high activity against OER and HER,with an overpotential of 283 m V at a current density of 40 m A cm^-2in OER and 155 m V at a current density of 10 m A cm^-2in HER.The nickel-molybdenum system tends to take NiSe₂as the main catalyst when OER is catalyzed,and will transform to its hydroxides and oxides,and MoS₂regulates the electronic structure of NiSe₂to improve the OER catalytic activity of NiSe₂.When carrying out HER catalysis,MoS₂tends to be the main body of catalysis,and NiSe₂regulates the electronic structure of MoS₂to promote the HER catalysis of MoS₂.The electrocatalytic total water decomposing performance of the above-mentioned materials is in the forefront of the reported catalysts.It provides ideas and references for the development of high-efficiency dual-function non-noble metal electrocatalysts that can be used in alkaline media.