Z-scheme photocatalyst systems employing Rh- and Ir-doped metal oxide materials for water splitting under visible light irradiation

Akihiko Kudo; Shunya Yoshino; Taichi Tsuchiya; Yuhei Udagawa; Yukihiro Takahashi; Masaharu Yamaguchi; Ikue Ogasawara; Hiroe Matsumoto; Akihide Iwase

doi:10.1039/c8fd00209f

Z-scheme photocatalyst systems employing Rh- and Ir-doped metal oxide materials for water splitting under visible light irradiation

Faraday Discuss. 2019 Jul 4;215(0):313-328. doi: 10.1039/c8fd00209f.

Authors

Akihiko Kudo¹, Shunya Yoshino², Taichi Tsuchiya², Yuhei Udagawa², Yukihiro Takahashi², Masaharu Yamaguchi², Ikue Ogasawara², Hiroe Matsumoto², Akihide Iwase¹

Affiliations

¹ Department of Applied Chemistry, Faculty of Science, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan. a-kudo@rs.kagu.tus.ac.jp and Photocatalysis International Research Center, Research Institute for Science and Technology, Tokyo University of Science, 2641, Yamazaki, Noda-shi, Chiba-ken 278-8510, Japan.
² Department of Applied Chemistry, Faculty of Science, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan. a-kudo@rs.kagu.tus.ac.jp.

PMID: 31017593
DOI: 10.1039/c8fd00209f

Abstract

Various types of Z-scheme systems for water splitting under visible light irradiation were successfully developed by employing Rh- and Ir-doped metal oxide powdered materials with relatively narrow energy gaps (EG): BaTa2O6:Ir,La (EG: 1.9-2.0 eV), NaTaO3:Ir,La (EG: 2.1-2.3 eV), SrTiO3:Ir (EG: 1.6-1.8 eV), NaNbO3:Rh,Ba (EG: 2.5 eV) and TiO2:Rh,Sb (EG: 2.1 eV), with conventional SrTiO3:Rh (an H2-evolving photocatalyst) or BiVO4 (an O2-evolving photocatalyst), and suitable electron mediators. The Z-scheme systems were classified into three groups depending on the combination of H2- and O2-evolving photocatalysts and electron mediator. The Z-scheme systems combining BaTa2O6:Ir,La with BiVO4, and NaTaO3:Ir,La with BiVO4 were active when a [Co(bpy)3]3+/2+ redox couple was used rather than an Fe3+/2+ one. The combination of SrTiO3:Ir with SrTiO3:Rh gave an activity when the [Co(bpy)3]3+/2+ and Fe3+/2+ redox couple ionic mediators were used. The Z-scheme systems combining NaNbO3:Rh,Ba and TiO2:Rh,Sb with SrTiO3:Rh showed activities by using the [Co(bpy)3]3+/2+ and Fe3+/2+ redox couples and also via interparticle electron transfer by just contact with/without reduced graphene oxide (RGO). These suitable combinations can be explained based on the impurity levels of doped Rh3+ and Ir3+ toward the redox potentials of the ionic mediators for the Z-scheme systems employing ionic mediators, and p-/n-type and onset potentials of the photocurrent in the photoelectrochemical properties of those photocatalyst materials for the Z-scheme systems working via interparticle electron transfer.