Nitrogen/fluorine-codoped rutile titania as a stable oxygen-evolution photocatalyst for solar-driven Z-scheme water splitting

Akinobu Miyoshi, Junie Jhon M. Vequizo, Shunta Nishioka, Yuma Kato, Muneaki Yamamoto, Shunsuke Yamashita, Toshiyuki Yokoi, Akihide Iwase, Shunsuke Nozawa, Akira Yamakata, Tomoko Yoshida, Koji Kimoto, Akihiko Kudo, Kazuhiko Maeda

Research output: Contribution to journalArticlepeer-review

25 Citations (Scopus)

Abstract

Nitrogen/fluorine-codoped rutile TiO2 (R-TiO2:N,F) was newly synthesized, and its photocatalytic activity for water oxidation was evaluated. R-TiO2:N,F could be prepared by nitridation of the rutile TiO2 (R-TiO2) and (NH4)2TiF6 mixture at 773 K. The prepared samples produced O2 from aqueous AgNO3 solution under visible light irradiation, while R-TiO2 nitrided at the same temperature without any fluorine source showed negligible activity. The highest activity was obtained with the sample prepared at the (NH4)2TiF6/R-TiO2 ratio of 15/85, exhibiting water oxidation activity even in the presence of a reversible electron acceptor such as IO3 - or Fe3+ with the aid of a RuO2 cocatalyst. Stoichiometric water splitting into H2 and O2 was achieved using a mixture of Ru/SrTiO3:Rh and RuO2/TiO2:N,F in the presence of [Co(bpy)3]3+/2+ (bpy = 2,2′-bipyridine) as a shuttle redox mediator without noticeable degradation of activity under visible light and even under AM1.5G simulated sunlight. Transient absorption spectroscopy revealed that appropriate nitrogen/fluorine codoping reduces the density of mid-gap states working as deep traps of photogenerated electrons, and increases the number of free electrons compared to only nitrogen-doped R-TiO2. Experimental results highlighted that the photocatalytic activity of R-TiO2:N,F could be enhanced by improving visible-light absorption capability through N/F codoping while suppressing the density of deep trap sites.

Original languageEnglish
Pages (from-to)2025-2035
Number of pages11
JournalSustainable Energy and Fuels
Volume2
Issue number9
DOIs
Publication statusPublished - 2018
Externally publishedYes

ASJC Scopus subject areas

  • Renewable Energy, Sustainability and the Environment
  • Fuel Technology
  • Energy Engineering and Power Technology

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