Green synthetic approach for Ti3+ self-doped TiO2−xnanoparticles with efficient visible light photocatalytic activity

Abstract

Rice-shaped Ti³⁺ self-doped TiO_2−x nanoparticles were synthesized by mild hydrothermal treatment of TiH₂ in H₂O₂ aqueous solution. The structure, crystallinity, morphology, and other properties of the as-prepared samples were characterized by X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microcopy and X-ray photoelectron spectra. Electron paramagnetic resonance spectra confirm the presence of high concentration of paramagnetic Ti³⁺ in the bulk and surface of the as-prepared samples. The particles showed a strong absorption across the UV to the visible light region and retained their light-blue color upon storage in ambient atmosphere or water for one month at 40 °C. The formation mechanism of Ti³⁺ self-doped TiO_2−x nanoparticles was discussed. Under visible light irradiation, the samples exhibit higher photocatalytic activity for hydrogen evolution and photooxidation of methylene blue than that of the commercial P25 TiO₂ nanoparticles. The sample obtained at 160 °C for 27 h showed a 9-fold enhancement for the visible light decomposition of methylene blue and 12.5 times higher for H₂ production in comparison to P25 TiO₂. The samples also showed an excellent cycling stability of the photocatalytic activity.