有缺陷的层状MoS_2复合TiO_2的光催化机理

Investigation on Enhanced Photocatalytic Mechanism of TiO_2 by Combined with Defective Layered MoS_2

采用第一性原理方法研究与有缺陷的层状MoS_2(d-MoS_2)复合后TiO_2的光催化性能增强的机理。结果发现,复合后体系更趋稳定。对TiO_2/d-MoS_2两相界面处的态密度和电荷差分密度进行分析,结果表明:复合后最低未占据分子轨道(LUMO)均由Mo4d轨道组成,最高占据分子轨道(HOMO)主要由S3p、O_2p轨道组成,电子由HOMO向LUMO跃迁。在光照射时,电子由TiO_2迁移到d-MoS_2,在界面处的d-MoS_2侧累积了多余的电子。电子在TiO_2与d-MoS_2之间的转移导致在界面间形成一个内极化电场,d-MoS_2的高电子传输性能使载流子很容易迁移,导致了光生电子和空穴的有效分离,有利于光催化性能的提高。

In this paper,First-Principles calculation based on density functional theory(DFT)was used to determinate the enhanced photocatalytic mechanism of TiO_2 by combinning with the defective layered MoS_2(d-MoS_2).The geometry structure and electronic properties,such as density of states,3 Dcharge density difference,have been investigated.And it revealed that TiO_2/d-MoS_2 composites could be stable in thermodynamics.Theoretical calculations showed that the lowest unoccupied molecular orbital(LUMO)of the composite was mainly composed of Mo4 dorbital,and the highest occupied molecular orbital(HOMO)was mainly composed of S3 p,O_2 p orbital.The electrons transit from HOMO to LUMO easily.Electrons migrated from TiO_2 to d-MoS_2 under irradiation,causing the electrons accumulated near the d-MoS_2 side.There appeared an internal polarized electric field,caused by the electrons transfer at the interface between TiO_2 and d-MoS_2.Additionally,the high electrons transport capability of d-MoS_2 made carriers migrate with ease,resulting in efficientseparation of photo-generated electrons and holes,which was favorable to the improvement of photocatalytic performance.