Preparation And Properties Of Molybdenum Sulfide/Cobalt Sulfide Electrocatalytic Hydrogen Evolution Composites

Hydrogen energy is considered to be the most sustainable and efficient clean energy because of its zero emission and low cost.Electrolyzed water hydrogen production technology is considered to be an effective method for large-scale hydrogen production,which requires electrocatalysts to reduce the overpotential of hydrogen evolution reaction（HER）.Precious metals such as platinum are still the most efficient electrochemical hydrogen evolution catalysts.However,the low reserves and high cost of precious metals seriously hinder its practical application.Therefore,the development of high-performance and low-cost catalysts is crucial to promote the application of electrochemical hydrogen evolution.In recent years,a large number of studies have been devoted to the design and preparation of non-precious metal electrocatalysts.Among them,molybdenum disulfide（MoS₂）has been highly expected to replace precious metal hydrogen evolution catalysts due to its low cost,high reserves,good stability,and hydrogen adsorption free energy close to Pt.However,the low conductivity and limited exposure of active sites of MoS₂ fundamentally limit the theoretical catalytic activity.In this paper,MoS₂ with different microstructure characteristics and cobalt sulfide composite heterostructure with high conductivity were constructed by heterogeneous interface regulation method.The hydrogen evolution performance of MoS₂ was significantly improved by the synergistic effect of heterogeneous interface and microstructure regulation.The main research contents and results are as follows:Co₃S₄-MoS₂ cobalt-molybdenum sulfide composite structure was prepared on stainless steel substrate by hydrothermal and high temperature sulfurization two-step method.The chemical composition,phase structure,microstructure characteristics and electrocatalytic hydrogen evolution behavior of the samples were studied.The results show that after the vulcanization reaction,Co₃S₄ and MoS₂ form a polyhedral uniform intermixed composite structure;electrochemical tests show that the electrochemical double-layer capacitance of Co₃S₄-MoS₂/SSF is 32%and 46%higher than that of MoS₂/SSF and Co₃S₄/SSF,respectively,that is,the active site density of the composite material is significantly higher than that of the single component structure.Under the synergistic effect of bimetallic sulfides,the hydrogen evolution activity of the composite electrocatalyst is significantly improved and has good stability.The square CoS₂/flaky MoS₂ nanocomposite structure was prepared by one-step hydrothermal method,and the influence mechanism of cobalt-molybdenum molar ratio on the microstructure and hydrogen evolution performance of the composite（CoS₂-MoS₂/SSF）was studied.The results of XPS and TEM show that the strong electronic interaction between MoS₂and CoS₂ promotes the O-H bond cleavage of H₂O molecules during the electrocatalytic process,which significantly improves the hydrogen evolution activity of the composite structure in acidic and alkaline electrolytes.Among them,the composite material prepared by the molar ratio of Co to Mo of 1:1 has the best electrochemical performance of the research system due to the more uniform distribution of nanosheets and the staggered growth of curved nanosheets,which expands the effective active area of the material.MoS₂@CoS₂/SSF core-shell heterostructures were prepared by pre-oxidation and hydrothermal two-step method using cobalt-based metal framework（Co-MOF）with large specific surface area as precursor.The microstructure characteristics,growth mechanism and electrocatalytic hydrogen evolution behavior in acidic and alkaline electrolytes were studied.The results show that the presence of Co-MOF not only effectively prevents the agglomeration of CoS₂,but also provides a large number of anchor points for the growth of MoS₂.The composite material forms a uniformly distributed sheet-like MoS₂@short rod-like CoS₂ core-shell heterostructure on the surface of the stainless steel fiber.Among them,MoS₂ forms a 1T-2H phase heterogeneous structure,which greatly increases the conductivity and effective active site density of the material.The short rod-like CoS₂ provides a high-speed charge transport channel,so that the electrocatalytic performance of the composite material is significantly improved compared with the single component.