Research On Electrocatalysis And Sodium Storage Performance Of Molybdenum Selenide-MXene Composite

MoSe₂ is considered to be an ideal electrocatalysis and sodium storage material due to its large number of active sites at the edge of unsaturated Se,large interlayer distance and easy diffusion of Na⁺.However,MoSe₂ tends to agglomerate and stack during the electrochemical process and has low inherent conductivity.Therefore,combining MoSe₂ with highly conductive materials is an effective method to improve electrochemical performance.As a two-dimensional material with high conductivity and large specific surface area,MXene exhibits excellent charge transfer kinetics during the hydrogen release process and has a low diffusion barrier to Na⁺.It is an ideal substrate composite material.Thence,in this paper,around MoSe₂ and MXene materials,a heterostructure of MoSe₂ and MXene coated with different carbon sources is constructed in order to ameliorate the problems of the materials in the electrochemical process and improve their electrocatalytic hydrogen evolution and sodium storage performance.The main research results are as follows:In order to improve the performance of the material in terms of electrochemical hydrogen evolution,a carbon-coated MoSe₂/Mo₂CT_x@C three-dimensional network composite material was successfully synthesized by using glucose as the carbon source and a one-step hydrothermal method.Mo₂CT_x as a conductive substrate effectively prevents the agglomeration of MoSe₂ nanosheets,improves the conductivity of the material and increases the number of hydrogen evolution sites.The strong interface coupling between MoSe₂,Mo₂CT_x and the carbon layer significantly improves the charge transfer rate.At the same time,the presence of the carbon layer further improves the conductivity of the material,and its high reducibility effectively prevents MXene from being oxidized and provides support for maintaining structural stability,effectively improving electrochemical hydrogen evolution activity and electrochemical stability.In order to achieve a current density of 10 m A cm^-2,only a overpotential of 108.3 m V drive is required,and it still maintains good electrochemical stability after a long-term cycle test and a chronoamperometric test.In order to improve the performance of the material in terms of sodium storage,a carbon-coated MoSe₂/Mo₂CT_x/C heterostructure material was successfully synthesized by using dopamine as a carbon source and using a combination of hydrothermal reaction and annealing.MoSe₂/Mo₂CT_x/C shows high specific capacity,excellent cycle performance and rate performance when used as sodium ion negative electrode.At a current density of 500 m A g^-1,a high reversible specific capacity of653.7 m A h g^-1 remains after 1700 cycles.It can be ascribed to the unique heterostructure that shortens the path for Na⁺diffusion and electron transport,and provides a larger contact area between the electrode and the electrolyte,thereby improving cycle stability and rate performance.The strong coupling between MoSe₂,Mo₂CT_x and the carbon layer and the barrier effect of the carbon layer greatly improve the structural stability of the material and increase electrons/ions transmission rate.Additionally,the high conductivity of MXene and the carbon layer improves the conductivity of the material and enhances the ion diffusion process between the MoSe₂ layers.Ihese greatly improve the specific capacity,cycle stability and rate performance of MoSe₂/Mo₂CT_x/C.