Ti-O共掺杂石墨烯的电子结构和光学性质的理论研究

Theoretical study on electronic structures and optical properties of Ti-O co-doped grapheme

本文利用基于密度泛函理论的第一性原理方法研究了本征石墨烯和不同掺杂浓度下Ti-O共掺杂石墨烯的电子结构和光学性质,并讨论了其内部的微观机制.研究结果表明:本征石墨烯是一种零带隙材料,狄拉克点在费米能级面上,其在紫外光区的光吸收强度较强.Ti-O共掺杂石墨烯可以很好的打开石墨烯的带隙和提高石墨烯的光催化强度,Ti18-O18@G模型费米能级附近的态密度主要由C-p轨道、Ti-d轨道和O-p轨道杂化而成.Ti18-O18@G模型在可见光区的吸收谱强度最大,主要归因于其内部晶格畸变、带隙被打开和杂质能带的出现,这些因素可以促进电子空穴对的产生和分离,从而使石墨烯在可见光区的光催化能力得到增强.本研究结果可为开发高催化活性的石墨烯提供理论依据.

In this paper,the electronic structures and optical properties of intrinsic graphene and Ti-O co-doped graphene with different doping concentrations are studied by first-principles method based on density functional theory. The internal microscopic mechanisms are discussed. The results are as follows. The intrinsic graphene is a zero direct band gap material,and the Dirac point is on the Fermi level. The light absorption intensity of intrinsic graphene is strong in the ultraviolet region. Ti-O co-doped graphene can open the band gap of graphene and increase the photocatalytic intensity of grapheme very well. The density of states of Ti18-O18@ G model,near the Fermi level,is mainly formed by hybridization of C-p orbital,Ti-d orbit and O-p orbit. The Ti18-O18@ G model has the largest absorption spectrum intensity in the visible region,which is due mainly to the internal lattice distortion,band gap opening and impurity band. These factors can promote the generation and separation of electron-hole pairs. Therefore,the photocatalytic ability of graphene in the visible region is enhanced. The conclusions of this paper can provide a theoretical basis for the development of graphene with high catalytic activity.