Theoretical Design And Modification Of Several Two-dimensional Materials

Due to the unique crystal structures and the novel physical and chemical properties,twodimensional(2D)materials exhibit great potential in electronics,spintronics,and single-atom catalysts(SACs).However,there are still challenges for the practical applications of 2D materials: first,it is difficult for the common 2D materials to simultaneously possess the advantages of high and anisotropic carrier mobility,strong spin-orbit coupling effect,and environmental stability,which limits the applications of 2D materials in high-performance electronics and spintronics;secondly,the experimental improvement of the chemical activity of 2D materials usually involves the process of trials and errors.There still lacks the understanding of the relationships between chemical activity and the complex coordination effects of SACs,which limits the efficient design of high-performance SACs.Generally,the improvement of the electronic performance and chemical activity of 2D materials depends on the regulation of the electronic structures of 2D materials,such as structure design,structural assembly,strain engineering,and doping of 2D materials.Therefore,based on density functional theory,we manage to tune the electronic properties and chemical activities of 2D materials by designing new 2D materials,strain engineering,and doping.The detailed research content is summarized in the following three parts:First,we theoretically design a novel tellurium-based 2D material,named tellurenyne.Different from the common 2D covalent network structure,tellurenyne is assembled from onedimensional helical tellurium chain(named telluryne)via van der Waals forces.Tellurenyne not only possesses high and anisotropic carrier mobility but also exhibits high environmental stability.In particular,by changing the phase order of the one-dimensional telluryne in tellurenyne,we can effectively control the optimal carrier type and the corresponding transport direction.In addition,tellurenyne has a significant Rashba-type spin-orbit coupling effect,which belongs to the giant Rashba system.Our results not only show that tellurenyne has the potential applications in advanced electronics and spintronics but also provide new prospects for designing new 2D materials.Based on the above research,we further explore the effect of strain on the electronic and transport properties of tellurenyne.Under the uniaxial strain,tellurenyne still maintains its unique one-dimensional chain based 2D structure and high stability.The uniaxial strain can effectively tailor the band structure of tellurenyne on a large scale.In particular,under the high tension strain along the telluryne direction,the Rashba effect of tellurenyne is enhanced significantly,belonging to the giant Rashba system.Moreover,the hole mobility along the telluryne direction is an order of magnitude higher than that of the phosphorene.Therefore,under the effect of strain,the tellurenyne exhibits the higher potential applications in electronics and spintronics.Superior to the structure design and strain engineering,doping can effectively improve the chemical activity of the original 2D materials,which exhibits great potential in the field of SACs.However,there still lacks the understanding of the relationships between the chemical activity and the complex coordination effects.A descriptor ψ based on the number of valence electrons and the electronegativity of the active center is applied to study the hydrogen evolution reaction on SACs.Descriptor ψ can describe the adsorption behavior of hydrogen and the activity of hydrogen evolution reaction on SACs.Descriptor ψ also reveals the coordination effects of active centers,such as the electronic structure,crystal structure of the doped atoms in bulk counterparts,the nitrogen dopant,and the periodicity of structure on the chemical activity of 2D materials.The doping strategy based on descriptor ψ provides a solid foundation for the design of SACs with high-performance.