Research On Preparation And Mechanism Of Two-dimensional Molybdenum Disulfide Functional Material By Liquid Phase Exfoliation

Two-dimensional molybdenum disulfide(2D-MoS2)has a graphene-like structure,consisted of mono-,fewer-nanosheets.Due to its excellent physical and chemical properties,2D-MoS2 has shown great application prospects in many fields such as energy,environment,biomedicine,and catalysis.The large-scale preparation and application of 2D-MoS2 become currently a research hotspot.Liquid phase exfoliation is an important method to achieve large-scale preparation of 2D-MoS2.However,there are still many problems with this method,which limits the subsequent application and development of 2D-MoS2.This paper has carried out a series of studies on the process,mechanism and product application of the liquid phase exfoliation for green and efficient construction of 2D-MoS2 and its carbon composite materials.The main contents are as follows:1.Preparation of 2D-MoS2 powder by the coagulation precipitation.First,the dispersion of 2D-MoS2 was prepared by liquid phase exfoliation and Triton X-100 as dispersant.The morphology of 2D-MoS2 was studied.Then,the simple,efficient and easy-to-scale preparation of 2D-MoS2 powder has been achieved via coagulation effect of strong electrolytes.In this process,2D-MoS2 powder did not undergo irreversible agglomeration and have a excellent dispersibility in N-methyl pyrrolidone(NMP),grease,pure water,methanol,ethanol,and isopropanol.2D-MoS2 powder has an ultrathin nanosheets structure,high crystallinity and a loose structure.The lateral size of 2D-MoS2 is less than 200 nm.The average lateral size is 110.4 nm.And the number of layers is 2-3.2D-MoS2 powder can be dispersed in various solvents at different concentrations as needed,which is beneficial to the subsequent application of 2D-MoS2.Due to its excellent dispersibility and abundant catalytic active sites,2D-MoS2 powder exhibits high catalytic activity in Fenton reaction.2.The preparation of 2D-MoS2 in low-boiling polar solvents has been achieved by solvothermal surface modification.The surface of modified MoS2 is attached with negatively charged hydrophilic clusters,which improves the dispersibility and exfoliating efficiency of MoS2 in low-boiling solvents.The effects of solvothermal modification on the hydrophilicity and liquid phase exfoliating efficiency of MoS2 were studied.2D-MoS2 has high crystallinity.The average lateral size is less than 160 nm.And the number of layers is less than 10 layers.The exfoliating efficiency and morphology of MoS2 in different low-boiling polar solvents were investigated.The exfoliating efficiency from high to low is:isopropyl alcohol,ethanol,methanol,and pure water.In this paper,the performance of 2D-MoS2 dispersion liquid directly used as hydrogen evolution catalyst for electrolyzed water was studied.When the current density is 10 mA·cm-2,the corresponding initial overpotential is-0.42 mV.And it has good catalytic stability.This method provides a new way to prepare low boiling point dispersion of 2D-MoS2.3.One-step in-situ preparation of 2D-MoS2/zero-dimensional carbon(0D carbon)composite materials by liquid phase exfoliation.Firstly,carbon nanospheres(CNSs)and carbon quantum nanodots(CQDs)were obtained by hydrothermal carbonization.Their sizes are about 41 nm and 2 nm,respectively.Due to the surface contains a large number of hydrophilic functional groups,CNSs and CQDs have excellent water dispersibility.The 2D-MoS2/CNSs and 2D-MoS2/CQDs composite materials were obtained by exfoliating bulk MoS2 in pure water using CNSs and CQDs as solid dispersants,respectively.The effects of pH value,initial concentration of bulk MoS2,exfoliating time,0D carbon concentration on liquid phase exfoliation and the structure of composite materials were studied.The average lateral size of 2D-MoS2 is less than 320 nm.And the number of layers is below 6 layers.The 2D-MoS2/0D carbon composite material has good dispersion stability in water.The mechanism of amphiphilic 0D carbon materials dispersing 2D-MoS2 was studied by experimental study and theoretical calculations,which proved that the 2D-MoS2 spontaneously combined with the hydrophobic region on 0D carbon.Hydrophilic groups(carboxyl groups,hydroxyl groups)ionize in water,which increases the surface charge of MoS2.The strong electrostatic repulsion between the nanosheets makes it able to exist stably.In this paper,0D carbon is used as solid dispersant to obtain graphene and 2D-WS2 with less defects,which confirmed the universality of this method.The 2D-MoS2/CQDs composite material as an adsorbent can efficiently adsorb methylene blue from an aqueous solution.This is an effective and scalable method for the in-situ preparation of 2D-MoS2/0D carbon composite materials.4.2D-MoS2/graphene oxide(GO)composite material was prepared in situ using GO as solid dispersant.The effects of pH,bulk MoS2 concentration and size,exfoliation time,and degree of oxidation of GO on liquid phase exfoliation were investigated.Characterization and analysis of 2D-MoS2/GO composite morphology structure and composition.2D-MoS2 uniformly adheres to the surface of GO.The average lateral size is 180.3 nm.And the number of layers is about 9.Theoretical calculations have investigated the mechanism by which GO can disperse MoS2.The results show that the hydrophobic region of GO can spontaneously combine with MoS2,while the hydrophilic region has weaker binding force with MoS2.2D-MoS2/reduced graphene oxide(RGO)composite film with porous structure was prepared by reduction and filtration.The morphology and structure of the 2D-MoS2/RGO film was studied and used as solid supercapacitor electrode material,showing excellent electrochemical performance.