Preparation And Electrochemical Performance Of Molybdenum Disulfide/carbon Composite Nanofibers

At present,clean and sustainable energy is the cornerstone for further economic and social development.Supercapacitors have been widely used in solar energy,wind power,new energy vehicles and power grids as energy storage devices.As a renewable and efficient clean energy source,hydrogen is one of the ideal solutions for future energy needs.Two-dimensional materials and their composite materials have attracted much attention due to their special structures and physical and chemical properties,and have achieved excellent performance in many fields such as energy storage,catalysis,and electronic information.In this paper,MoS₂/graphene nanosheets embedded in activated carbon nanofibers?MoS₂@G/AC₂?are fabricated through an electrospinning process followed by pretreatment,KOH activation and carbonization.Then,to explore the structural-activity relationship between the structure of MoS₂/graphene/activated carbon nanofibers and their electrochemical properties.The details are as follows:?1?In the experiment,MoS₂/carbon nanofibers were prepared with polyacrylonitrile and polyvinylpyrrolidone as carbon sources,respectively,and the effect of carbon source composition on the distribution of molybdenum disulfide was studied by molecular simulation techniques.The results show that MoS₂ was a multi-layer stack state in MoS₂/C₁nanofibers which prepared with polyacrylonitrile as carbon sources.While,due to the stronger interaction between the layer structure of MoS₂,N and O doped graphite,MoS₂was a single-layer stack state in MoS₂/C₂ nanofibers which prepared with polyvinylpyrrolidone as carbon sources.Further,MoS₂/AC₂ nanofibers with graphene were prepared by KOH activation which has a large number of microporous structures on the surface and greatly enhance its specific surface area.Regulating the content of Mo S₂ in composite nanofibers,the results show that specific surface area and volume of composite nanofibers were increased with the enhance of MoS₂ in the certain range.But excess of MoS₂ will inhibit the activation of composite nanofibers by KOH.?2?To explore the effects of structure and constituents on composite nanofibers'electrochemical properties when the composite nanofibers as electrode materials of supercapacitors and catalysists of hydrogen evolution reaction.The results show that the composite nanofibers have rich microporous structure on the surface.On the one hand,the specific surface area of the material was improved,which is conducive to ion transport and charge storage.On the other hand,the more MoS₂ in composite nanofibers were exposed to the surface,which can further improve the pseudo-capacitance of the composite nanofiber and provide more catalytic active sites for hydrogen evolution reaction.Then,the electrochemical performance of MoS₂@G/AC₂ nanofibers with a monolayer of MoS₂ was better than others.As an electrode material for supercapacitors,MoS₂@G/AC₂ nanofibers shown the specific capacitance reaches 301 F g^-1 and 246.3 F g^-1at 1 A g^-1 and 10 A g^-1,respectively,and capacitance retention with 83.8%after 5000 cycles charge-discharge.As a catalyst for the hydrogen evolution reaction,the overpotential of the MoS₂@G/AC₂nanofibers was 201 mV at a current density of 10 mA cm^-2.After 1000 cycles of voltammetry tests,the LSV changed very little and showed good stability.