Solar Water Oxidation by a Visible‐Light‐Responsive Tantalum/Nitrogen‐Codoped Rutile Titania Anode for Photoelectrochemical Water Splitting and Carbon Dioxide Fixation

• Published in: ChemPhotoChem 2019-01, Vol.3 (1), p.37-45
• Main Authors: Nakada, Akinobu, Uchiyama, Tomoki, Kawakami, Nozomi, Sahara, Go, Nishioka, Shunta, Kamata, Ryutaro, Kumagai, Hiromu, Ishitani, Osamu, Uchimoto, Yoshiharu, Maeda, Kazuhiko
• Format: Article
• Language: English
• Subjects: artificial photosynthesis; carbon dioxide reduction; doped TiO2; photoelectrochemistry; water splitting
• ISSN: 2367-0932; 2367-0932
• DOI: 10.1002/cptc.201800157

Non‐oxide materials such as oxynitrides are good candidates as photoanodes for visible‐light‐driven water oxidation, but most of them suffer from oxidative degradation by photogenerated holes, resulting in low stability. Herein we developed a photoanode using a visible‐light‐responsive TiO2 powder doped with tantalum and nitrogen (TiO2:Ta/N) for water oxidation. The Ta/N codoping enabled a stable anodic photocurrent response attributable to water oxidation under visible‐light irradiation. Surface modification of the TiO2:Ta/N anode with RuOx species further facilitated water oxidation catalysis, achieving stable O2 evolution over 5 h of operation with no sign of deactivation. Operando XAFS measurements revealed an important function of the RuOx species as a collector of photogenerated holes in TiO2:Ta/N, facilitating the photoelectrochemical water oxidation. Visible‐light‐driven H2 evolution and solar‐driven CO2 reduction into CO were both achieved by using water as an electron donor in photoelectrochemical cells with the TiO2:Ta/N photoanode coupled to a Pt cathode and a Ru(II)–Re(I) binuclear complex photocathode, respectively. Jack of all trades: A photoanode composed of TiO2 doped with tantalum and nitrogen worked for stable photoelectrochemical water oxidation coupled to hydrogen evolution and carbon dioxide reduction under visible and solar light. Operando XAFS measurements revealed a key function of RuOx species as a collector of photogenerated holes in TiO2:Ta/N, facilitating the photoelectrochemical water oxidation.