title: Crystal Structure, Electronic Structure, and Photocatalytic Activity of Oxysulfides: La2Ta2ZrS2O8, La2Ta2TiS2O8, and La2Nb2TiS2O8.
abstract: The novel oxysulfides La2Ta2ZrS2O8 (LTZSO), La2Ta2TiS2O8 (LTTSO), and La2Nb2TiS2O8 (LNTSO) were synthesized, and their crystal structures, electronic structures, and photocatalytic activities for water splitting under visible light were investigated. Density functional theory calculations showed that these compounds are direct-band-gap semiconductors. Close to the conduction band minimum, the main contribution to the band structure comes from the d orbitals of Zr or Ti ions, while the region near the valence band maximum is associated with the 3p orbitals of S ions. The absorption-edge wavelength was determined to be 540 nm for LTZSO and 700 nm for LTTSO and LNTSO. An analysis of the crystal structure using synchrotron X-ray diffraction revealed that these compounds contained antisite defects at transition metal ion sites, and these were considered to be the origin of the broad absorption at wavelengths longer than that corresponding to band-gap excitation. LTZSO was revealed to be active in the oxygen evolution reaction from aqueous solution containing a sacrificial electron acceptor under visible-light illumination. This result was supported by the band alignment and flat-band potential determined by photoelectron spectroscopy and Mott-Schottky plots.
authors.affiliation: Department of Chemical System Engineering, School of Engineering, The University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Goto
authors.affiliation: Department of Chemical System Engineering, School of Engineering, The University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: Jeongsuk
authors.initials: J
authors.lastname: Seo
authors.affiliation: Department of Chemical System Engineering, School of Engineering, The University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: Kazunori
authors.initials: K
authors.lastname: Kumamoto
authors.affiliation: Department of Chemical System Engineering, School of Engineering, The University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Hisatomi
authors.affiliation: Department of Electrical and Electronic Engineering, Tokyo Metropolitan University , Hachioji 192-0397, Japan.
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Mizuguchi
authors.affiliation: Department of Applied Physics and Physico-Informatics, Faculty of Science and Technology, Keio University , Yokohama 223-8522, Japan.
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Kamihara
authors.affiliation: Department of Chemical System Engineering, School of Engineering, The University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: Masao
authors.initials: M
authors.lastname: Katayama
authors.affiliation: Department of Chemical System Engineering, School of Engineering, The University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.|JST, PRESTO , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Minegishi
authors.affiliation: Department of Chemical System Engineering, School of Engineering, The University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: Kazunari
authors.initials: K
authors.lastname: Domen