摘要
在密度泛函理论的基础上,系统地研究了Cu/N(共)掺杂的TiO_2/MoS_2异质结体系的几何结构、电子结构和光学性质.计算发现, TiO_2/MoS_2异质结的带隙相比于纯的TiO_2(101)表面明显变小, Cu/N(共)掺杂TiO_2/MoS_2异质结体系的禁带宽度也明显地减小,这导致光子激发能量的降低和光吸收能力的提高.通过计算Cu/N(共)掺杂TiO_2/MoS_2的差分电荷密度,发现光生电子与空穴积累在掺杂后的TiO_2(101)表面和单层MoS_2之间,这表明掺杂杂质体系可以有效地抑制光生电子-空穴对的复合.此外,我们计算了在不同压力下TiO_2/MoS_2异质结的几何、电子和光学性质,发现适当增加压力可以有效提高异质结的光吸收性能.本文结果表明, Cu/N(共)掺杂TiO_2/MoS_2异质结和对TiO_2/MoS_2异质结加压都能有效地提高材料的光学性能.
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 3 d 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.
作者
王冠仕
林彦明
赵亚丽
姜振益
张晓东
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)
出处
《物理学报》
SCIE
EI
CAS
CSCD
北大核心
2018年第23期36-47,共12页
Acta Physica Sinica
基金
国家自然科学基金(批准号:11447030,51572219)
陕西省自然科学基金(批准号:2016JQ1038,2015JM1018)
西北大学科学基金(批准号:14NW23)
西北大学双级一流大学建设项目资助的课题.
关键词
杂化泛函
电子结构
掺杂
光学性质
hybrid functionals
electronic structures
doping
optical properties
