The Study Of Ti₃C₂ And Ti₂C By First-principle Caluculation

Ti₃C₂ and Ti₂C are novel materials with graphene-like structure,this material have good physical and chemical properties,That means it will have broad application prospects.However,the current research is mainly about multi-layer structure of Ti₃C₂ and Ti₂C,and there is no unified understanding of the mechanism and theory of adsorption of Ti₃C₂ and Ti₂C.In this paper,the density functional theory?DFT?was used to explore the electrical and adsorption properties about the single layer structure of Ti₃C₂ and Ti₂C.Firstly,the monolayer models of Ti₃C₂ and Ti₂C and the monolayer models of Ti₃C₂T_X and Ti₂CT_X?T=H,O,F and OH?have been established,it is proved that the3d orbital electrons of Ti atoms make the reducibility of Ti₃C₂ and Ti₂C.The adsorption energies of H,O,F and OH on the surface of Ti₃C₂ and Ti₂C were calculated,it was confirmed that the surface of Ti₃C₂ and Ti₂C prepared by experiments were generally covered with O,F and OH.It is proved that the surface group change the electrical properties of Ti₃C₂ and Ti₂C,electron transfer exists in Ti₃C₂ and Ti₂C,and Ti₃C₂?OH?₂,Ti₂CO₂ and Ti₂CF₂ are converted into semiconductors.It is also found that there exists dirac cone in the metastable structure of Ti₂CF₂,Other Ti₃C₂ and Ti₂C covered with surface groups have similar dirac cone structure.Secondly,the models of the single layer structure of Ti₃C₂ and Ti₂C with different coverage and different proportions of surface groups were established.The effects of different coverage and different proportion surface groups on the structure of Ti₃C₂ and Ti₂C were less.The results showed that the lower the surface group coverage,the larger the adsorption energies of O,F and OH for Ti₃C₂ and Ti₂C.The essence is the electron transfer of the Ti atom,which leads to the increase of the average electron number of the surface groups.At the same time,different surface groups can also change the electrical properties of Ti₃C₂ and Ti₂C.When the proportion of O,F and OH is the same,Ti₃C₂ and Ti₂C are converted into semiconductors.Lastly,the adsorption structure models of Li,Na and K on the surface of single-layer Ti₃C₂ and Ti₃C₂T₂?T=O,F and OH?and Ti₂C and Ti₂CT₂?T=O,F and OH?have been established.The adsorption of Li,Na and K affects the structure of Ti₃C₂ and Ti₂C.It has been found that the surface groups affect the adsorption energies of Li,Na and K for Ti₃C₂ and Ti₂C,and the most stable adsorption sites of Li,Na and K in Ti₃C₂ and Ti₂C structures were changed.