One-step synthesis of nonstoichiometric TiO2 nanorod films for enhanced photocatalytic H2 evolution

Abstract

The realization of one-dimensional nanostructures or Ti³⁺ self-doping in TiO₂ photocatalysts has proven to be an effective approach for significantly improving their photocatalytic performance. Herein, a series of nonstoichiometric anatase TiO₂ nanorod films were deposited at 50–500 °C by a facile one-step magnetron sputtering method. The correlation between the microstructures and the photocatalytic H₂ production abilities of the films was studied. It is found that, by increasing the deposition temperature, the as-sputtered TiO₂ grains transformed from quasi-spherical to rod-like structures while the concentration of the Ti³⁺ species decreased gradually. Thus, by virtue of the collaboration between nanostructure engineering and defect engineering, the sample deposited at 300 °C showed a maximum H₂ generation rate of 1874 μmol m⁻² h⁻¹, which was about 134 times higher than that of a Degussa P25 powder film (14 μmol m⁻² h⁻¹). Furthermore, the stoichiometric TiO₂ shell formed on the surface of TiO₂ nanograins protected the defective TiO_2−x core from further oxidation, resulting in an excellent photocatalytic stability of the films. The possible film growth and photocatalytic reaction mechanisms over the Ti³⁺ doped TiO₂ nanorod films have been investigated. Our work provides a facile route to fabricating a high-efficiency defect-based TiO₂ or other transition metal oxide nanostructures with a controlled morphology for solar energy conversion.