| 2D material begins to play an important role in the field of material science since graphene was found in experiment in 2004.Graphene is composed of in-plane Carbon atoms with strong sp2 hybridized orbitals.Compared to bulk graphite,graphene exhibit excellent physical properties,like ultra-high carrier mobility,excellent optical properties and high heat conduction properties.However,since the gapless features of graphene,it hugely restricts the application of graphene in the field of switching device,photocatalysis and so on.Researchers begin to explore experimentally or theoretically other novel 2D material,such as TMDs,h-BN,Phosphorene,Mxene and so on.The related research field are more and more extensive,like photocatalysis in water splitting,solar battery,Topological Insulators(T1),Spin-electron device.2D materials are widely applied in the field of photocatalysis in water splitting.Compared with traditional 3D photocatalytic materials,2D material has its distinctive advantages,like larger surface area,more active sites in the surface,higher carrier mobility and better separation of carriers,which greatly enhance the efficiency of photocatalysis.However,qualified 2D photocatalyst for water splitting needs to satisfy the requirement of band gap and band edge positions,transportation and separation of photo-generated carriers,currently,the proved 2D photocatalyst is limited both in experiment and theoretical.Hence,looking for the efficient 2D photocatalytic materials for water splitting is an essential work in the field of computational material science.2D layered materials,which can be isolated from layered bulk with the method of mechanical exfoliation,is an important part of 2D mater:ials.Because of the relatively weaker van der Waals interaction between layers,it is feasible to get the monolayer and few layered material by physical or chemical exfoliation from the bulk in experiment Based on above discussion,we use first-principle calculation to investigate the electronic property and potential application of monolayer MX2(X=N,M=Be,Mg)and Hf(Zr)GeTe4.The conclusion is as follows:Chapter 1:Introduction of the research background and current research of 2D nanomaterials.Chapter 2:Introduction of related theoretical base of first-principle calculation and common calculation software.Chapter 3:Predict two monolayers of BeN2 and MgN2 with hexagonal honeycomb construction using first-principle calculation,and predict it to be potential visible-light response 2D photocatalyst for water spitting.We systematically investigate the stability,electronic properties,optical properties,and carrier transportation properties.Suitable bandgap and band edge position ensure the potential application in photacatalysis for water splitting.At the same time,BeN2 has ultra-high electrons mobility,which facilitate the electrons to move to the surface of material quickly and participate the reduction reaction.In addition,the great difference between the mobility of electrons and holes means good separation effect,which reduce the possibility of recombination of carriers.Chapter 4:Systematically investigate the electronic properties and regulation of exerted strain to the electronic properties of HfGeTe4 and ZrGeTe4.The bulk of the two materials are layered construction,and the adjacent layers are connected by weak Van der Waals function.Thus,the monolayer is available by mechanical exfoliation in experiment,the calculation of energy of exfoliation provides sufficient evidence.The result shows that both structures are semiconductor with band gap of about 0.7eV.The mechanical property shows great flexibility of ZrGeTe4,which means that ZrGeTe4 can withstand great transformation.The study of transportation of carriers shows that both materials gain high electron mobility.Furthermore,it can achieve transformation from semiconductor to metal,and direct band gap to indirect band gap with suitable strain. |
