Research On Surface Modification Of Two-dimensional Materials And Their Catalytic And Adsorption Characteristics

Two-dimensional materials possess high carrier mobility,large specific surface area,good electric conduction performance and many other outstanding features,which make them have extensive application prospect in the lithium-ion batteries,electrochemical hydrogen evolution reaction,gas sensing and other fields.Among them,graphene is the most typical.In 2004,graphene was successfully exfoliated.Because of its distinctive physical,chemical,optical and electronic properties,scientists and workers in the industry carried out extensive and in-depth research.After that,various kinds of graphene-like two-dimensional materials have been studied successively.Among them,as a kind of typical two-dimensional material,phosphorene possesses layered structure,which is similar to that of graphene,the good anisotropic conductivity and direct band gap structure make it have a very good applications in the electron devices and electrochemical sensing.However,it is unstable that the physical adsorption in the field of gas adsorption,which limit the practical applications in the field of methanol adsorption and sensing.Another two-dimensional material which is widely studied is molybdenum disulphide,which belongs to the transition metal sulfide,also has a layered structure which is similar to that of graphene.The marginal sulfur atoms of molybdenum disulphide have the electrocatalytic performances of hydrogen evolution reaction and could be used as an electrocatalyst material.However,as a semiconductor material,molybdenum disulphide has poor intrinsic conductivity.Moreover,due to the effect of van der Waals force,molybdenum disulfide nanoparticles are easy to reunite,which limits their applications in electrocatalytic hydrogen evolution reaction.This thesis is based on the surface modification of two dimensional materials,by heteroatom doping and lithium-ion embeding to regulate the charge distribution of the surface and the whole conductivity of the two-dimensional materials,and research their applications in the field of methanol gas adsorption and electrocatalytic hydrogen evolution reaction.Specifically,the following research work have been carried out:?1?First-principles calculations based on density functional theory were employed to investigate the adsorption of methanol gas molecule on pristine and X-doped phosphorene?X=B,C,N and O?.In the adsorption model,the CH₃OH gas molecule was placed on the top of different phosphorene surfaces,O-H bond of CH₃OH was parallel to phosphorene surfaces,and the whole adsorption systems were fully optimized by Vienna ab initio simulation package.The calculation results demonstrated that heteroatom doping could effectively regulate the charge distribution of the phosphorene surfaces and affect the adsorption properties of phosphopene to methanol gas molecules.The N and O doping improved the adsorption performances of phosphorene to CH₃OH gas molecule,while B and C doping were almost not beneficial compared to the pristine phosphorene.This work suggested that N-doped and O-doped phosphorene are ideal candidates used for CH₃OH gas sensing,which provides a very valuable reference for methanol gas adsorption and the design of sensor based on phosphorene-based materials.?2?Using the commercial MoS₂ powder as raw material,lithium chloride monohydrate as a source of lithium,embedding the lithium-ion into molybdenum disulfide material to improve the conductivity through mechanical ball milling dispersion method so as to enhance the electrocatalytic performances of hydrogen evolution reaction.The results demonstrated that embedding the lithium-ion could not only improve the conductivity of MoS₂ electrocatalyst,but also realize the transformation from 2H semiconductor phase to 1T metal phase.Based on the above two factors,the electrocatalytic performances of lithiated MoS₂ for hydrogen evolution reaction were significantly improved compared with commercial MoS₂.