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A Redox‐Mediator‐Free Solar‐Driven Z‐Scheme Water‐Splitting System Consisting of Modified Ta3N5 as an Oxygen‐Evolution Photocatalyst |
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| Authors: | Su Su Khine Ma Prof Kazuhiko Maeda Dr Takashi Hisatomi Masashi Tabata Prof Akihiko Kudo Prof Kazunari Domen |
| Institution: | 1. Department of Chemical System Engineering, The University of Tokyo, 7‐3‐1 Hongo, Bunkyo‐ku, Tokyo 113‐8656 (Japan), Fax: (+81)?3‐5841‐8838;2. Department of Chemistry, Graduate School of Science and Engineering, Tokyo Institute of Technology, 2‐12‐1‐NE‐2 Ookayama, Meguro‐ku, Tokyo 152‐8550 (Japan);3. Department of Applied Chemistry, Faculty of Science, Science University of Tokyo, 1–3 Kagurazaka, Shinjuku‐ku, Tokyo 162‐8601 (Japan) |
| 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 (CoOx) was found to be the most effective, improving the water‐oxidation efficiency of Ta3N5 by six to seven times. Further modification of CoOx/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. |
| Keywords: | artificial photosynthesis photooxidation photosynthesis semiconductors tantalum |