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

Rice-shaped Ti3+ self-doped TiO2−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 TiO2−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.