Morphology Control Of Molybdenum Disulfide/Carbon Composite For Efficient Electrocatalytic Hydrogen Evolution

With the continuous development of industrialization,the energy crisis and environmental pollution become serious problems.The use of renewable energy sources is of vital importance.Electrocatalytic Hydrogen Evolution technology has the advantages of large hydrogen production and low energy consumption,which is considered an effective way to realize sustainable development,so it is critical to dvelope new and high efficiency catalysts.As a typical non-precious metal type catalyst,MoS₂ has attracted more and more attention in the field of hydrogen evolution catalysis due to its excellent physical and chemical properties.However,MoS₂ is a semiconductor with poor conductivity,which is obviously disadvantageous for electrocatalytic hydrogen evolution.In order to overcome this defect,molybdenum disulfide as the active material,starting from its multi-functional orientation,was used to study the performance of hydrogen evolution reaction.The main research contents and results are as followings:（1）A 3D sponge-like structure of molybdenum disulfide/reduced graphene oxide composites were successfully prepared through a facile one-spot hydrothermal route,where graphene were used as the matrix and MoS₂ were used as the main active materials.This preparation method allows MoS₂ to uniformly grow on the surface of the grapheme with a large number of pore structures.Such structure endows the hybrid can not only prevent the restacking of graphene nanosheets and the aggregation of MoS₂ nanosheets during the electrolytic processes,but also provide abundant active edge sites for HER.Finally,we can draw the concilusion that the molybdenum disulfide/reduced graphene oxide hybrid,the molar ratio of graphene reachs 15 wt%,exhibits a low overpotential of 97 mV and a low Tafel slope of 70mV dec^-1,therefore the composite takes advantage of excellent stabilition.（2）Co-doped molybdenum disulfide/reduced graphene oxide composites were successfully prepared by in-situ doping under hydrothermal conditions.We have explored the structural morphology and the trends in HER activity of materials by the means of XRD,Raman,BET,SEM,TEM,XPS and electrochemical tests.It was found that a proper amount of Co doping can introduce defects,which is beneficial to activate the inert surface of MoS₂.Benefiting from those structures,the promotion effects of the transition metal doped MoS₂ can be increased the specific surface area of the material and exposed more catalytic active sites.In addition,Co doping can effectively avoid the agglomeration and accumulation of MoS₂ nanosheets without changing the original morphology of the composite,which makes the MoS₂nanosheets slightly thinner and more curved.At a current density of 10 mA cm^-2,the overpotential of the composite reached 77 mV,the Tafel slope was 60 mV dec^-1.It can be observed that its polarization curve after continuous 1,000 th cycle is similar to the initial one,suggesting that the hybrids have good long-term stability.（3）In the third part,Co-doped MoS₂ nanosheets with vertical alignment on carbon cloth were successfully designed by hydrothermal synthesis,where carbon cloth was used as the conductive matrix material.The MoS₂ nanosheet in situ grew to link the carbon cloth support,which was formed a porous structure.The vertical growth of MoS₂ nanosheets,Co doping and self-supporting carbon cloth structure work together to make CC-MC composites exhibit excellent electrocatalytic hydrogen evolution performance in both 1 M KOH and 0.5 M H₂SO₄ solutions.Electrochemical tests showed that the overpotential of the composite is 68 mV and 57mV respectively at a current density of 10 mA cm^-2,and the Tafel slopes are 60 mV dec^-1 and 54 mV dec^-1,respectively.What’s more,the carbon cloth itself can provide a limiting environment for the growth of MoS₂ and shorten the transmission distance of the electrolyte with the large specific surface area and three-dimensional structure.In addition,as a support substrate,carbon cloth has good electrical conductivity and independence,which can accelerate the electron transport of materials and reduce the charge transfer resistance.