First Principle Investigation On Catalytic Pyrolysis Of Water For Hydrogen Evolution Reaction By MoS₂

As a hydrogen evolution catalyst,molybdenum disulfide has developed for a period of time.However,it has not received wide attention and application due to its poor catalytic.With the rising of two-dimensional nanomaterials research led by graphene,monolayer molybdenum disulfide has been attracting worldwide attention again.And the Current studies show that the hydrogen evolution catalytic sites of the perfect monolayer molybdenum disulfide are extremely limited and are confined to the edge atoms.The inert surfaces seriously restrict the catalytic performance of the materials.Therefore,the theoretical study further reveals that cavity defects can be introduced into these inert surfaces to enhance their catalytic activity.Based on the first-principle calculation method,this work focused on the enhancement effect of surface vacancy defects on water dissociation and hydrogen production of monolayer molybdenum disulfide.The results are helpful to promote the spreading and application of monolayer molybdenum disulfide as catalyst for hydrogen evolution from water dissociation.Firstly,this paper introduces the structure,preparation method,defects,application prospects of monolayer molybdenum disulfide,and the basic principles of electrolysis of water and hydrogen evolution.The density functional theory and first-principles calculation methods are briefly described,and the calculation software used in this paper is briefly introduced.Based on the first-principles calculation method,we systematically studied the single atom adsorption and diffusion behavior of monolayer of molybdenum disulfide,mainly involving hydrogen,lithium,sodium and magnesium atoms.Adsorption studies have shown that the perfect monolayer of molybdenum disulfide for hydrogen adsorption process is endothermic and has a high adsorption energy.And the stable adsorption height is lowest.The adsorption process of the other three metal atoms is exothermic,and the adsorption energy of lithium,sodium,magnesium and other atoms decreases in turn,and they are all smaller than the hydrogen adsorption energy.Their stable adsorption distance increases in turn and is larger than the hydrogen adsorption height.Diffusion studies have shown that the diffusion barriers of lithium,sodium,magnesium and other atoms on the surface of molybdenum disulfide are successively reduced and are all lower than the potential barrier of atom through the molybdenum disulfide.The results of this study will help to understand the theoretical basis for the application of monolayer molybdenum disulfide in lithium-sodium-magnesia plasma batteries.In order to fully explore the catalytic activity for the hydrogen evolution of monolayer molybdenum disulfide break down the water,the effects of six kinds of vacancy defect types were studied in this paper.Firstly,the effects of defects on their lattice structure and electrical properties were studied.Then,systematically studies of the adsorption of water molecules on a single layer of molybdenum disulfide vacancy defects are conducted.It is revealed that MoS2 with two types of defects(VMo and VMoS2)have catalytic ability to cleave water for hydrogen evolution.Through electronic projection state density and charge transfer analysis studies,the electronic distribution and transfer characteristics of the catalytic properties of these two defect types were elucidated.The results also showed that the VMo-SLMoS2 needs to absorb energy when it cracks water,while the VMos2 releases heat.By analyzing the hydrogen evolution performance of Vacancy-SLMoS2,it was found that the hydrogen evolution activity of VMo-SLMoS2 is high,but it is still not superior to the catalytic activity of metallic platinum.Therefore,to further improve the hydrogen evolution catalytic activity of VMo-SLMoS2,the influence of the strain engineering on the catalytic activity of the atoms surrounding the cavity was studied.The results show that the uniaxial stretching does not optimize the hydrogen evolution performance of the VMo-SLMoS2,which is obviously different from the conclusion that the Vs-SLMoS2 hydrogen evolution activity can be optimized and improved by uniaxial stretching.However,further studies have found that biaxial compression can further enhance the hydrogen evolution catalytic performance of VMo-SLMoS2.And its hydrogen evolution catalytic performance is optimal under 4.5%compressive strain.The charge analysis results show that the effect of strain on the catalytic activity of the VMo-SLMoS2 hydrogen evolution is achieved by changing the interaction between the sulfur atom around the hole and the molybdenum atom.The results of this study will contribute to the development of monolayered molybdenum disulfide catalysts with excellent hydrogen evolution catalytic performance and promote the development of hydrogen energy.