Modulation Of Nearly Free Electron States Inhydroxyl-Functionalized MXenes:A First-Principles Study

Since 2004,two scientists at the University of Manchester,AndreGeim and Konstantin Novoselov,successfully used micromechanical exfoliation to separate graphene from graphite.The research of two-dimensional materials is relatively fiery.MXene,which was first discovered by Drexel University,is one of the twodimensional materials.MXene material is obtained through MAX materials,M is some transition metal elements,A refers to some main group elements,and X stands for C or N.Because the binding force between A and M and X is relatively weak,A can be removed by using the method such as chemical etching and then peel it to obtain MXene.MXene materials have many excellent properties,such as good electrical conductivity,short ion transmission path,large specific surface area,and strong stability.The application fields are also very broad,such as supercapacitors,lithium ion secondary batteries,as adsorption materials,hydrogen storage materials,lubricants,and as catalysts for hydrogen production from water.Therefore,MXene materials are of great research value.We find that in MXene materials,there are many nearly free electronic states.Although nearly free electronic states are common,such as in graphene,there are also nearly free electronic states,but because the nearly free electronic state of graphene is relatively far from the Fermi level of graphene,it does not affect the physical chemistry of graphene.Therefore,the study of graphene generally does not study its nearly freely electronic state.However,the MXene materials are different.Their nearly free electron states are very close to the Fermi level,which has a great impact on the properties of the MXene materials.We can even try to change the performance of the MXene materials by regulating the nearly free electron state in the MXene material.Therefore,it is necessary for us to study the nearly free electronic states in MXene materials.The main contents of this article include the following:1.First-principles calculations based on density functional theory were used to study the effect of applied voltage on the nearly free electronic state.2.Introducing the image potential and solving the Schr?dinger equation to establish the wave function of the nearly free electronic state.And by studying the nature of the wave function,understand the effect of the interlayer distance on the electronic structure.3.The nearly free electronic state can be controlled by changing the interlayer distance,thereby affecting the topological properties of the electronic structure of MXene materials.