Transparent Nb-doped TiO2 films with the [001] preferred orientation for efficient photocatalytic oxidation performance

Doping and tailoring of the crystal orientation are two main strategies to improve the photocatalytic properties of TiO2 films. Herein, we introduce a novel route for obtaining Nb-doped TiO2 anatase films with the [001] preferred orientation by thermal oxidation of the [100]-oriented Nb-doped TiN film prepared by magnetron sputtering. Comprehensive analyses with X-ray diffraction, Raman scattering, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy indicate that the proportion of high-energy (001) facets of the Nb-doped TiO2 film is more than 90% and the Nb5+ ion is successfully doped into the film without destroying the crystallinity and orientation. Moreover, the Nb5+ ion doping significantly restrains the growth of the TiO2 grains and increases the surface roughness, and consequently increases the surface-reactive sites. Therefore, the as-fabricated Nb-doped TiO2 film exhibits efficient photocatalytic oxidation performance for acetaldehyde and oleic acid decomposition under simulated solar light irradiation. Such Nb-doped TiO2 anatase films with high-reactivity (001) facet exposure may find applications in the photocatalysis and solar energy conversion fields.