title: A redox-mediator-free solar-driven Z-scheme water-splitting system consisting of modified Ta3N5 as an oxygen-evolution photocatalyst.
abstract: Tantalum nitride (Ta3N5) modified with various O2-evolution cocatalysts was employed as a photocatalyst for water oxidation under visible light (λ>420 nm) in an attempt to construct a redox-mediator-free Z-scheme water-splitting system. Ta3N5 was prepared by nitriding Ta2O5 powder under a flow of NH3 at 1023-1223 K. The activity of Ta3N5 for water oxidation from an aqueous AgNO3 solution as an electron acceptor without cocatalyst was dependent on the generation of a well-crystallized Ta3N5 phase with a low density of anionic defects. Modification of Ta3N5 with nanoparticulate metal oxides as cocatalysts for O2 evolution improved water-oxidation activity. Of the cocatalysts examined, cobalt oxide (CoO(x)) was found to be the most effective, improving the water-oxidation efficiency of Ta3N5 by six to seven times. Further modification of CoO(x)/Ta3N5 with metallic Ir as an electron sink allowed one to achieve Z-scheme water splitting under simulated sunlight through interparticle electron transfer without the need for a shuttle redox mediator in combination with Ru-loaded SrTiO3 doped with Rh as a H2-evolution photocatalyst.
authors.affiliation: Department of Chemical System Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: Su Su Khine
authors.initials: SS
authors.lastname: Ma
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Maeda
authors.forename: Takashi
authors.initials: T
authors.lastname: Hisatomi
authors.forename: Masashi
authors.initials: M
authors.lastname: Tabata
authors.forename: Akihiko
authors.initials: A
authors.lastname: Kudo
authors.forename: Kazunari
authors.initials: K
authors.lastname: Domen