关键词: 杂化泛函/
电子结构/
掺杂/
光学性质
English Abstract
Electronic and optical performances of (Cu, N) codoped TiO2/MoS2 heterostructure photocatalyst: Hybrid DFT (HSE06) study
Wang Guan-Shi,Lin Yan-Ming,
Zhao Ya-Li,
Jiang Zhen-Yi,
Zhang Xiao-Dong
Shaanxi Key Laboratory for Theoretical Physics Frontiers, Institute of Modern Physics, Northwest University, Xi'an 710069, China
Fund Project:Project supported by the National Natural Science Foundation of China (Grant Nos. 11447030, 51572219), the Natural Science Foundation of Shaanxi Province, China (Grant Nos. 2016JQ1038, 2015JM1018), the Science Foundation of Northwest University, China (Grant No. 14NW23), and the Double First-class University Construction Project of Northwest University, China.Received Date:12 August 2018
Accepted Date:29 September 2018
Published Online:05 December 2018
Abstract:Anatase titanium dioxide (TiO2) has attracted much attention due to its excellent photocatalytic properties. However, the band gap of anatase TiO2 is 3.2 eV, which can absorb only about 4% of the ultraviolet light (λ < 400 nm). Molybdenum disulfide (MoS2) is a new layered two-dimensional compound semiconductor, and it has been widely studied for its preferably optical absorption and photocatalytic properties. Moreover, the high recombination rate of photoexcited electron-hole of monolayer MoS2 leads to low photocatalytic efficiency. In this work, based on Heyd-Scuseria-Ernzerhof (HSE06) hybrid density functional theory, the geometric structure, electronic structure, optical properties, charge transfer and effect of pressure on structure of Cu/N doped TiO2/MoS2 heterostructures are systematically studied. The interface interaction between anatase TiO2(101) surface and monolayer MoS2 shows that TiO2 and MoS2 form a van der Waals heterostructure. The defect formation energy is calculated to demonstrate that Cu@O&N@O is the most stable codoping site. The result of the density of states shows that the band gap of TiO2/MoS2 heterojunction is 1.38 eV, which is obviously smaller than that of the pure anatase TiO2(101) surface (2.90 eV). The band gap of Cu/N doped TiO2/MoS2 heterojunction obviously decreases, and an impurity band provided by Cu 3d orbitals appears in the forbidden band, which leads to the decrease of the photon excitation energy and the enhancement of the optical absorption capacity. The x-y planar averaged and three-dimensional charge density difference of Cu/N doped TiO2/MoS2 are also calculated. It is found that there are electrons' and holes' accumulation in the doped anatase TiO2(101) surface and the single layer MoS2, showing that the Cu/N doping can effectively reduce the recombination of the photoexcited electron hole pairs. Calculated optical absorption spectra show that Cu/N doped TiO2/MoS2 system has obvious improvement in the absorption of visible light. In addition, we calculate the geometrical, electronic and optical absorption spectra of TiO2/MoS2 heterojunction under different pressures. The results show that the appropriate increase of pressure can effectively improve the optical absorption properties of heterojunction and Cu/N doped TiO2/MoS2 heterojunction and TiO2/MoS2 heterojunction can effectively improve the optical properties of the material. These findings are helpful in understanding the photocatalytic mechanism and relevant experimental observations.
Keywords: hybrid functionals/
electronic structures/
doping/
optical properties
