Physicochemical Effects on Photocatalytic Water Oxidation by Titanium Fluorooxynitride Powder under Visible Light

• Published in: Chemistry of materials 2009-06, Vol.21 (11), p.2286-2291
• Main Authors: Maeda, Kazuhiko, Lee, Byongjin, Lu, Daling, Domen, Kazunari
• Format: Article
• Language: English
• Subjects: Catalysis and Catalysts; Inorganic Solids and Ceramics; Photosensitive Materials
• ISSN: 0897-4756; 1520-5002
• DOI: 10.1021/cm9005162

Titanium fluorooxynitride (TiN x O y F z ) powder prepared by thermal treatment of NH4TiOF3 with NH3 or N2 is examined as a photocatalyst for water oxidation to form molecular oxygen under visible light (λ > 420 nm). Nitridation of NH4TiOF3 under NH3 flow at 773 K for durations longer than 0.5 h results in the production of well-crystallized TiN x O y F z particles with an anatase crystal structure and a broad absorption band in the vicinity of 530 nm. The as-prepared materials exhibit good activity for O2 evolution from aqueous solution under visible light in the presence of silver nitrate as an electron acceptor. Although thermal treatment of NH4TiOF3 under N2 flow in a similar manner also yields TiN x O y F z , the as-prepared material exhibits only a small photon absorption shoulder at 400−500 nm consistent with the low nitrogen content of the product. The experimental results indicate that enhanced photocatalytic activity in this system requires suppression of the production of reduced titanium species, which act as electron−hole recombination centers, and the generation of high nitrogen content to obtain a broad response in the visible light band.