Construction Of MoS₂ Heterostructure And Study On Its Electrocatalytic Hydrogen Production Performance

With the proposal of my country’s"dual carbon"goal and the emergence of energy,environment,and climate issues,it is urgent to replace traditional fossil energy with clean and sustainable energy.Hydrogen energy has the advantages of high combustion calorific value,non-polluting combustion products,and abundant raw material storage.It is an ideal substitute for traditional fossil energy.In particular,the use of intermittent renewable energy such as solar energy and wind energy to generate hydrogen from electrolyzed water has unique advantages.Energy consumption in hydrogen production by electrolysis of water accounts for more than80%of the total cost,and its slow kinetics is an important reason for the water splitting voltage to be higher than the theoretical voltage and energy consumption to increase.Therefore,it is of great significance to reduce the cost of hydrogen production by using suitable catalysts to reduce the overpotential of hydrogen production from water electrolysis to improve energy conversion efficiency and stability.As traditional precious metal catalysts such as Pt,Ru O₂,Ir O₂ and other precious metals have few resources and high prices,which hinder their large-scale commercial application,it is of great significance to develop cheap,stable and abundant non-precious metal catalysts to replace precious metals for the application and promotion of electrocatalytic hydrogen production technology.Molybdenum disulfide（MoS₂）has a hydrogen adsorption energyΔG_H close to that of Pt,and is an ideal catalyst for the hydrogen evolution reaction（HER）.MoS₂ mainly has two main crystal phases,2H and 1T,among which the 1T phase has a unique electronic structure and high electrical conductivity,and the 1T phase nanosheets have abundant active sites on both the edge and the basal plane,showing significantly better performance than Hydrogen production activity of the 2H phase.However,there are still difficulties in the synthesis of MoS₂,especially the high-concentration 1T phase,and the overpotential of HER is significantly higher than that of industrialized HER catalysts.The research focus of this paper is to explore new synthesis techniques to achieve direct growth of 1T-MoS₂ on carbon cloth（CC）,while increasing the content of 1T phase with higher catalytic activity,and then forming heterostructures by combining other hydrogen-producing catalysts,to obtain highly active MoS₂ heterostructure HER electrocatalysts.This paper proposes a synthesis technique for directly growing MoS₂ nanosheets with high hydrogen production activity by supercritical method.By exploring the influence of synthesis process parameters on the phase composition and morphology of MoS₂ nanosheets,the growth mechanism of MoS₂ is clarified;through the tests of electrochemical properties such as CV,LSV and ECSA,the growth mechanism and process parameters affect the HER of MoS₂@CC influence on catalytic performance.On this basis,Ni（OH）₂ nanosheets were deposited on1T/2H-MoS₂@CC by electrochemical deposition technique to construct a heterostructure to further its HER catalytic performance.The following research conclusions were obtained through the research:（1）By testing and analyzing the morphology,composition and electrochemical properties of MoS₂ nanosheets hydrothermally synthesized under various parameters（S/Mo molar ratio,solution concentration and hydrothermal synthesis temperature）,the hydrothermal synthesis of MoS₂ under this reaction system was obtained.The optimal process parameters of nanosheets,the concentration of Mo source is 2.1 m M,S/Mo=4:1,and the hydrothermal synthesis temperature is 220℃.The study found that MoS₂@CC synthesized under this system has a relative balance of defects and resistance brought about by relatively moderate crystallinity,MoS₂ has a higher loading rate on CC,and the synthesized sample has a higher specific surface area and The electrochemically active area,the HER overpotential tested in 1 M KOH solution is 175 m V@10 m A·cm^-2,the Tafel slope is 96.82 m V·dec^-1,and the ECSA area is 13.96m F·cm^-2.（2）In the above hydrothermal system,tetramethylammonium hydroxide（TMAH）was basically added to introduce the large cation TMA⁺,and the supercritical heterogeneous nucleation and growth of MoS₂ nanosheets directly on the carbon cloth was achieved by optimizing the addition of TMA⁺.It was found that the MoS₂nanosheets grown by supercritical heterogeneous nucleation had a 1T/2H mixed-phase structure,in which the content of 1T phase was 88%,and the interlayer of 1T phase was expanded and distorted due to the insertion of TMA⁺large cations.1T/2H-MoS₂@CC exhibits excellent HER activity,with hydrogen production overpotentials of 167 m V@10 m A·cm^-2（1 M KOH）and 135 m V@10 m A·cm^-2（0.5M H₂SO₄）,constant current at 100 m A·cm^-2 It can run stably for more than 100 h.（3）Using 1T/2H-MoS₂@CC as a template,Ni（OH）₂/1T/2H-MoS₂/@CC heterostructure was constructed by electrochemical deposition of Ni（OH）₂.The effects of deposition potential（-1.12V,-1.24 V,-1.4 V）and deposition time（100 s,200 s,500 s,1000 s,2000 s）on the morphology,structure and electrochemical performance of heterostructures were systematically studied,and the most The best deposition parameters are deposition potential of-1.24 V,deposition time of1000s,HER overpotential of 40 m V@10 m A·cm^-2（1 M KOH）,and current density of 887m A·cm^-2 at an overpotential of 476 m V,and It can run stably for more than 72 h at 100m A·cm^-2.The 1T/2H-MoS₂@CC catalyst synthesized by the supercritical heterogeneous nucleation growth technology developed in this paper has excellent electrocatalytic activity and stability,and greatly reduces the consumption of raw materials and synthesis costs.By the construction of 1T/2H-MoS₂/Ni（OH）₂@CC heterostructure,the catalytic performance is better than that of commercial Pt/C electrodes.The threshold of industrialization application of electrolytic water hydrogen production is greatly reduced.