Brookite TiO 2 , the latest TiO 2 photocatalyst, promises to be an interesting candidate for photocatalytic applications because of its unique physical and chemical properties. In this study, pure-phase brookite TiO 2 with a quasi-spherical nanostructure was successfully synthesized via a solvothermal method using tetrabutyl titanate (Ti(OC 4 H 9 ) 4 , TBOT) as the Ti source in the presence of oxalic acid. NaOH was used to regulate the pH of solution. The structure and morphology of the samples were then analyzed using multiple methods, such as X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) measurements and ultraviolet-visible diffuse spectroscopy (UV-Vis). Photocatalytic activities of the as-synthesized brookite TiO 2 were evaluated by degrading aqueous methylene blue solution under UV light irradiation. The effect of thermal treatment temperature on photocatalytic activity of the samples was also investigated. The produced brookite TiO 2 nanopowders calcined at 500 °C for 2 h showed the highest photocatalytic activity, and the corresponding degradation rate of methylene blue (10 mg/L) reached 96.7% after 90 min of illumination. In addition, the formation mechanism of pure-phase brookite TiO 2 was investigated. It was found that the formation of pure-phase brookite TiO 2 in this study was ascribed to the combined action of oxalic acid and sodium hydroxide.

Cu-doped TiO2 having a brookite phase and showing enhanced visible light photocatalytic activity was synthesized using a mild solvothermal method. The as-prepared samples were characterized by various techniques, such as X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, UV-Vis diffuse reflectance spectroscopy. Photocatalytic activity of Cu-doped brookite TiO2 nanoparticles was evaluated by photodegradation of methylene blue under visible light irradiation. The X-ray diffraction analysis showed that the crystallite size of Cu-doped brookite TiO2 samples decreased with the increase of Cu concentration in the samples. The UV-Vis diffuse reflectance spectroscopy analysis of the Cu-doped TiO2 samples showed a shift to lower energy levels in the band gap compared with that of bare phase brookite TiO2. Cu doped brookite TiO2 can obviously improve its visible light photocatalytic activity because of Cu ions acting as electron acceptors and inhibiting electron-hole recombination. The brookite TiO2 sample with 7.0 wt.% Cu showed the highest photocatalytic activity and the corresponding degradation rate of MB (10 mg/L) reached to 87 % after visible light illumination for 120 min, much higher than that of bare brookite TiO2 prepared under the same conditions (78 %).

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