Oxysulfide Sm 2 Ti 2 S 2 O 5 as a Stable Photocatalyst for Water Oxidation and Reduction under Visible Light Irradiation (λ ≤ 650 nm)

作者：Akio Ishikawa, Tsuyoshi Takata, Junko N. Kondo, Masahiko Hara, Hisayoshi Kobayashi, Kazunari Domen · 发表于：Journal of the American Chemical Society · 年份：2002 · DOI：10.1021/ja0269643 · 被引用次数：1041 · 研究领域：Advanced Photocatalysis Techniques、Chalcogenide Semiconductor Thin Films、Electrocatalysts for Energy Conversion

A Ti-based oxysulfide, Sm(2)Ti(2)S(2)O(5), was studied as a visible light-driven photocatalyst. Under visible light (440 nm < or = lambda < or = 650 nm) irradiation, Sm(2)Ti(2)S(2)O(5) with a band gap of approximately 2 eV evolved H(2) or O(2) from aqueous solutions containing a sacrificial electron donor (Na(2)S-Na(2)SO(3) or methanol) or acceptor (Ag(+)) without any noticeable degradation. This oxysulfide is, therefore, a stable photocatalyst with strong reduction and oxidation abilities under visible-light irradiation. The electronic band structure of Sm(2)Ti(2)S(2)O(5) was calculated using the plane-wave-based density functional theory (DFT) program. It was elucidated that the S3p orbitals constitute the upper part of the valence band and these orbitals make an essential contribution to the small band gap energy. The conduction and valence bands' positions of Sm(2)Ti(2)S(2)O(5) were also determined by electrochemical measurements. It indicated that conduction and valence bands were found to have satisfactory potentials for the reduction of H(+) to H(2) and the oxidation of H(2)O to O(2) at pH = 8. This is consistent with the results of the photocatalytic reactions.