Intercalation-Detonation Exfoliation Mechanism And Application Research Of Graphene-like MoS₂ And Nanocomposites

As an important two-dimensional layered nano material,graphene-like molybdenum disulfide(GL-MoS₂)has a wide range of applications in many fields,such as lubrication,catalysis,energy storage,optoelectronic devices and so on,with its unique sandwich structure and excellent physical properties.At present,there are many kinds of method to prepare graphene-like MoS₂,but there are some problems,such as cumbersome technology,low preparation efficiency,poor repeatability and difficult mass production.By improving the existing methods or developing new methods,it is urgent to prepare graphene-like MoS₂ materials to meet the requirements of electronic devices or electronic chips with smaller specifications and higher energy efficiency,especially in the field of optoelectronic devices and energy storage materials.Therefore,it is urgent to develop and promote the controllable key technology for the preparation of graphene like MoS₂and its nanocomposites with two-dimensional layered structure.In this paper,layered graphene-like MoS₂ materials were successfully prepared by a new intercalation-detonation method combining oxidation intercalation and high-energy explosive reaction stripping.By optimizing the intercalation and explosion process,the controllable preparation of graphene-like MoS₂ material was realized,and the reaction mechanism of oxidation intercalation and high energy explosion stripping was revealed.Because of its unique layered structure,MoS₂ can be intercalated by insert ions or groups between the layers,which can change the interlayer spacing and van der Waals force.Therefore,the oxidation intercalation of MoS₂ was realized by inserting oxygen-containing groups between the layers of MoS₂ with strong oxidants.The structure-activity relationship was established by characterization methods to evaluate and analyze the intercalation efficiency,and the influence of the adding time of deionized water in the intercalation process on the intercalation efficiency was explored.The mechanism of increasing intercalation efficiency by continuously adding warm deionized water in the heating and holding stage of medium and high temperature was revealed.Based on the theory of explosion impact,the change of molecular structure in the process of detonation was analyzed.Combined with the evaluation and analysis of products obtained by different explosion ratios,the optimal explosion ratio of 1:1 between explosive and MoS₂ material was obtained,and the controllable preparation of high-quality graphene like MoS₂ was realized.Through the establishment of explosion molecular structure model,the mechanism of high-energy explosion stripping reaction was revealed.On the one hand,high-energy detonation forms high-speed shock wave to cut and separate MoS₂ sheet.On the other hand,the explosive decomposition of picric acid produces a large number of gases,which react with oxygen-containing groups at high temperature under the induction of explosion to generate CO₂ and H₂O.The gases generated expand between the MoS₂ layers.With the impact of high-energy explosion,the MoS₂ materials are finally stripped into single or few layers of graphene like MoS₂materials.The results of characterization analysis of intercalation-detonation exfoliation MoS₂products show that the prepared graphene like MoS₂ has good crystal structure and obvious layered structure,and there are bends and folds at the edge,which belongs to less layer(within 10 layers)graphene-like MoS₂ materials.In order to study the universality of high-energy detonation exfoliation method for the preparation of two-dimensional materials,this method is applied to exfoliate bulk WS₂ and h-BN materials,and the results show that the prepared graphene-like MoS₂ materials have good crystal structure and obvious layered structure The results show that single-layer WS₂ material and few layer graphene like h-BN material are successfully obtained by high-energy explosive stripping,which indicates that this method has a wide application prospect in the field of two-dimensional material stripping.The graphene-like MoS₂ materials were characterized by magnetometer and magnetic microscope.The results show that the graphene-like MoS₂ material prepared by the intercalation-detonation method has obvious ferromagnetism,and the saturation magnetization MS reaches 0.01 at 300 K Based on the analysis of the structure of MoS₂,it is concluded that the magnetic source of MoS₂ is the high-density edge and surface defects produced in the explosion process,and the local magnetic moment is generated,so as to obtain a strong magnetic response signal.The first principles based on density functional theory are used to analyze the original MoS₂,single-layer MoS₂ and S-defect MoS₂ The results of structure and magnetic simulation show that the surface S-defect MoS₂ exhibits metallic properties,and has the highest magnetic moment and energy difference between non-magnetic state and magnetic state.The results verify the conjecture that the magnetic properties of graphene-like MoS₂ materials prepared by intercalation-detonation are derived from the high density distribution edge and surface defects produced by detonation.Combine with the abundant catalytic sites of intercalated explosive graphene like MoS₂and the structural stability of carbon nanotube(CNT),graphene-like MoS₂/CNT nanocomposites were prepared by liquid phase synthesis.The electrocatalytic hydrogen evolution properties of graphene-like MoS₂ and MoS₂/CNT nanocomposites were tested.The results show that graphene like MoS₂/CNT nanocomposites have excellent catalytic activity The results show that the polarization overpotential is 77 m V and Tafel slope is32.2 m V dec^-1 at the current density of 10 m A cm^-2,and the electrocatalytic performance is close to that of commercial Pt/C catalyst.Based on the first principles of density functional theory,the electronic structure and hydrogen adsorption of monolayer MoS₂/CNT composite structure are simulated.The results show that the electronic structure of graphene like MoS₂ is changed by the composite CNT material,and the catalytic effect of MoS₂ and CNT is synergistic,which improves its hydrogen adsorption ability.Moreover,the composite of CNT material improves the conductivity of graphene like MoS₂ material,which further improves the hydrogen adsorption efficiency.In addition,MoS₂ is easier to adsorb H atoms at Mo sites,which also verifies the conjecture that MoS₂ materials with high density edge and surface defects expose a large number of Mo catalytic sites,thus greatly improving the catalytic hydrogen evolution performance of MoS₂ materials.Therefore,it is an effective strategy to prepare MoS₂ with high defect density by intercalation explosion method and composite with CNT to improve the catalytic activity of MoS₂ for hydrogen evolution.