Ab initio density functional theory calculation of La5Ti2Cu1−xAgxS5O7 solid solution semiconductor photocatalysts for water splitting. (16th May 2017)

• Record Type: Journal Article
• Authors: Sakata, Kaoruho; Hisatomi, Takashi; Goto, Yosuke; Magyari-Köpe, Blanka; Deák, Peter; Yamada, Taro; Domen, Kazunari
• Is Part Of: Journal of physics. Volume 50:Number 23(2017)
• Publication Date: 2017-05-16
• Subjects: DFT calculation -- band structure -- effective mass -- solid solution -- photocatalyst; Physics -- Periodicals; 530
• DOI: 10.1088/1361-6463/aa6f77
• Languages: English
• ISSNs: 0022-3727

Abstract

Abstract: La5 Ti2 Cu1− x Ag x S5 O7, a solid solution of La5 Ti2 CuS5 O7 and La5 Ti2 AgS5 O7, is a semiconductor studied for sunlight-driven water splitting. In this study, the band structure and effective mass of La5 Ti2 Cu1− x Ag x S5 O7 solid solutions are analyzed on the basis of density functional theory (DFT) calculations to reveal the effect of the composition on the band structure and the anisotropy in the conductivity. The band gap of La5 Ti2 Cu1− x Ag x S5 O7 materials exhibits a bowing with respect to the value of x . The effective masses of holes and electrons in La5 Ti2 Cu1− x Ag x S5 O7 are estimated from the band structure. Both holes and electrons have smaller effective masses in the b -axis direction than in the other directions, testifying the highly anisotropic electronic properties. The wave functions at the valence band maximum and the conduction band minimum are both delocalized along the b -axis only, forming parallel channels for electron and hole conduction. These results support the experimental observation that photoexcited carriers tend to migrate one dimensionally. The outcome of the theoretical calculation is qualitatively consistent with the experimental observations and helps to understand the electronic properties of La5 Ti2 Cu1− x Ag x S5 O7 with varying compositions.