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Article

Role of Ag⁺ in the Band Structures and Photocatalytic Properties of AgMO₃ (M: Ta and Nb) with the Perovskite Structure

Hideki Kato,^† Hisayoshi Kobayashi,^‡ and Akihiko Kudo*^†

Department of Applied Chemistry, Faculty of Science, Science University of Tokyo, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan, and Department of Chemistry and Bioscience, Faculty of Chemical Technology, Kurashiki University of Science and the Arts, 2640 Nishinoura, Tsurajima, Kurashiki 712-8505, Japan

J. Phys. Chem. B, 2002, 106 (48), pp 12441–12447

DOI: 10.1021/jp025974n

Publication Date (Web): November 12, 2002

†

Science University of Tokyo.

‡

Kurashiki University of Science and the Arts.

To whom correspondence should be addressed. E-mail: a-kudo@rs.kagu.tus.ac.jp. Fax: +81-33235-2214.

Abstract

Photophysical and photocatalytic properties of perovskite-type materials AgMO₃ (M: Ta and Nb) consisting of Ag⁺ and d⁰ ions were investigated. The band gaps of AgTaO₃ and AgNbO₃ were 3.4 and 2.8 eV, respectively, being 0.6 eV smaller than the band gaps of NaTaO₃ (4.0 eV) and NaNbO₃, even if the crystal structures of AgMO₃ were similar to those of NaMO₃. It was found from the electronic band structure study, using the plane-wave-based density functional method, that a hybrid orbital of Ag 4d and O 2p formed a valence band at a more negative level than O 2p orbitals. AgTaO₃ showed photocatalytic activity for pure water splitting into H₂ and O₂ under UV-light irradiation. AgNbO₃ has arisen as a new visible-light-driven photocatalyst possessing the ability to evolve H₂ or O₂ from water in the presence of sacrificial reagents.