Study On The Supercapacitor Properties Of The Molybdenum Disulfide/three-dimensional Graphene Composite

More and more environmental pollution problems（such as global warming and haze）have been brought a driving force for reducing dependence on the fossil fuels.At present,it is generally believed that the best energy source for production should come from renewable and sustainable resources（such as solar energy,wind energy,and ocean energy）.This has prompted relevant talents in the energy field to actively explore and research in the areas of energy conversion and energy storage.In clean energy technology,electrochemical technology is considered to be the most feasible,for its characteristics of environment friendly,sustainable development.Supercapacitors have attracted attention due to the high power density,long cycling ability,and low maintenance costs.Supercapacitors mainly rely on the electrolyte ion adsorption and desorption at both ends of electrodes.It can be divided to double layer capacitors and pseudocapacitor capacitors according to the mechanism of energy storage.The electrode material of supercapacitor not only needs good electrical conductivity,but also the microscopic structure of the electrode material.That is,the increased effective activity of surface area can short the distance of the electrolyte ions transmission and then the capacitance performance are improved.At present,the market mainly uses carbon materials as the electrode material of the supercapacitors,but the different structures of electrode materials express different electrochemical properties.A reasonable structural of the electrode material are designed for improving the capacitance performance of the supercapacitor,which has fully used the active surface of the electrode material.Monolayer/less-layered molybdenum disulfide（MoS₂）nanosheets possess graphene-like two-dimensional structures,and three-dimensional graphene（3DG）provides a large active specific surface area and high electrical conductivity.In this paper,two-dimensional monolayer/less-layered MoS₂ nanosheets dispersions were prepared by liquid phase exfoliation;3DG was prepared by chemical vapor deposition（CVD）.The two-dimensional MoS₂ nanosheets are vertically attached to the surface on the three-dimensional graphene,and the composite product is denoted as MoS₂/3DG.Scanning electron microscopy（SEM）,Raman spectroscopy（Raman）,X-ray diffraction（XRD）,X-ray photoelectron spectroscopy（XPS）,and other methods were used to test the structure and composition of the samples.Electrochemical workstations were used to carry out the electrochemical performance of the samples.The structural test results show that the obtained sheet of molybdenum disulfide nanosheets is vertically attached to the surface of 3DG.When the MoS₂ concentration was 0.20 mg L^-1,the MoS₂ nanosheets were vertically loaded on the inner and outer surfaces of 3DG,and the composite(MoS₂(0.20mg L^-1)/3DG)exhibited the best capacitance performance(specific capacitance reached 2182.33 mF cm^-2).After 5000 cycles of continuous charge and discharge tests,the specific capacitance of the MoS₂/3DG was maintained to116.83%(2,549.62 mF cm^-2).When the current density increased by 100 times(1 mA cm^-2-100 mA cm^-2),its specific capacitance retained 78.9%(2549.62 mF cm^-2-2011.65 mF cm^-2).At the same time,after assembling the device,a higher energy density(23.81 Wh m^-2)was obtained.The considerable electrochemical performance of MoS₂/3DG is attributed to:Vertical crosslinking Mo S₂/3DG composite towards high the contact area with the electrolyte and provides more unsaturated bonds and increases the electron and ion transmission efficiency;3DG as the base material of the electrode material,the conductivity of the electrode is improved and its three-dimensional rack structure further expands the specific surface area of the electrode material and shortens the transmission distance of the electrolyte ions.The considerable electrochemical performance of MoS₂/3DG reveals its good application prospects.