First-Principles Study On The Physical Properties Of Two-Dimensional MXenes Materials And Heterojunctions

In 2004,the graphene material made by mechanical peeling method opened the door of two-dimensional material to the world.At the same time,it breaks the restraint that the material with two-dimensional structure cannot exist stably under limited temperature.Subsequently,a large number of new two-dimensional materials,such as transition metal nitrides and carbides?MXenes?,hexagonal boron nitride,transition metal dihalides?TMDs?,silicones,etc.appeared one after another.In particular,the two-dimensional transition metal carbides or carbonitrides?MXenes?discovered in 2011 are not only similar in morphology to Graphene with high specific surface area,but also have a controllable change in surface functional group structure and differentiated Chemical composition,etc.,so MXenes materials with good performance can be applied to new energy fields such as energy storage,adsorption,electrochemistry,etc.However,the independent two-dimensional material structure is usually subject to various unfavorable restrictions in practical applications.Researchers try to use two or more such materials to construct a van der Waals heterostructure through the van der Waals force between the layers.The interface effect formed between different materials improves the properties of the materials,so as to realize its application value well.In this paper,the first-principles are used to study the selected MXenes materials and the physical properties of the heterojunction.The conclusions are summarized as follows:?1?Some intrinsic MXenes materials have excellent electrical conductivity and stable adsorption characteristics for metal particles.In order to further explore its performance as an energy storage material,we chose two-dimensional Ti₂C materials and two-dimensional materials such as Ti O₂,Ti Cl₂and the like with the same surface structure,through the use of first-principles calculation and comparative study of its adsorption of lithium ions as electrode materials.Discussed in detail,the optimal adsorption site of Li⁺ions on the surface of the monolayer,the diffusion path of lithium atoms was studied by the method of NEB?nudge elastic band?.In the calculation results,the Ti₂C,Ti O₂two-dimensional material lithium ion has an ultra-high theoretical capacity,which is attributed to its large specific surface area and surface adsorption sites,rapid lithium diffusion rate,excellent electronic conductivity,and low operating voltage,Is a promising LIB anode material.?2?Through first-principles calculations,we constructed heterojunctions of TMDs,two-dimensional chalcogenides,MXenes materials,etc.,and explored their basic physical properties and performance as photocatalysts.The physical properties of TMDs and two-dimensional layered sulfides are closely related to the structural morphology.The physical properties exhibited at different thicknesses and temperatures are different.Investigation of the heterojunctions of the Mo X₂-WX₂series with the same lattice constant and K point of symmetry shows that the overall change trend of VBM and CBM is the same as the upward trend of lattice constant.The heterojunction composed of mutual S element materials such as Mo S₂,WS₂and Sn S₂exhibits type II alignment at the angle of energy band alignment.Different preparation methods of MXenes materials lead to the presence of functional groups with uneven spatial distribution on the surface,and the binding energy of-O among the many functional groups covered on the surface has the greatest thermal stability.We built a Mo S₂/Ti₃C₂O₂heterojunction to enhance the stability of a single layer of Mo S₂as a photocatalyst,while also avoiding the effects of light pollution on the material.We have further explored the basic physical properties of the new MXenes material and its heterojunctions through first-principles calculations,and found extensive applications in the field of energy storage and photocatalysis.Through these studies,we hope to promote more breakthrough research on the properties of the MXenes family of materials.