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

Abstract

Abstract 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 TiO 2 powder doped with tantalum and nitrogen (TiO 2 :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 TiO 2 :Ta/N anode with RuO x species further facilitated water oxidation catalysis, achieving stable O 2 evolution over 5 h of operation with no sign of deactivation. Operando XAFS measurements revealed an important function of the RuO x species as a collector of photogenerated holes in TiO 2 :Ta/N, facilitating the photoelectrochemical water oxidation. Visible‐light‐driven H 2 evolution and solar‐driven CO 2 reduction into CO were both achieved by using water as an electron donor in photoelectrochemical cells with the TiO 2 :Ta/N photoanode coupled to a Pt cathode and a Ru(II)–Re(I) binuclear complex photocathode, respectively.