Photocatalytic Hydrogen Evolution Activity of Nitrogen/Fluorine-Codoped Rutile TiO(2)

[Image: see text] The development of a photocatalyst capable of evolving H(2) from water under visible light is important. Here, the photocatalytic activity of N/F-codoped rutile TiO(2) (TiO(2):N,F) for H(2) evolution was examined with respect to metal cocatalyst loading and irradiation conditions. Among the metal species examined, Pd was the best-performing cocatalyst for TiO(2):N,F under UV–vis irradiation (λ > 350 nm), producing H(2) from an aqueous methanol solution. The H(2) evolution activity was also dependent on the state of the loaded Pd species on the TiO(2):N,F, which varied depending on the preparation conditions. Pd/TiO(2):N,F prepared by an impregnation–H(2) reduction method, showed the highest performance. However, the activity of the optimized Pd/TiO(2):N,F toward H(2) evolution from an aqueous methanol solution was negligibly small under visible-light irradiation (λ > 400 nm), although the use of an ethylenediaminetetraacetic acid disodium salt as an electron donor resulted in observable H(2) evolution. Transient absorption spectroscopy revealed that although a relatively large population of reactive electrons was generated in the TiO(2):N,F under 355 nm UV-pulse photoexcitation, the density of reactive electrons generated under 480 nm visible light was lower. This wavelength-dependent behavior in photogenerated charge carrier dynamics could explain the different photocatalytic activities of the TiO(2):N,F catalysts under different irradiation conditions.