Tailored preparation of titania with controllable phases of anatase and brookite by an alkalescent hydrothermal route

Abstract

Titanium dioxide (TiO2) with different ratio of anatase to brookite has been selectively synthesized by an alkalescent hydrothermal treatment of TiCl3 in the presence of different concentration of NaCl. The resulting powders have been characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), photoluminescence (PL) analysis, UV–vis diffuse reflectance spectra (DRS), and Brunauer–Emmett–Teller (BET) analysis. The contents of anatase and brookite have been successfully controlled by adjusting the NaCl concentration and NH4OH/H2O volume ratio. The photocatalytic activity of TiO2 has been assessed by the degradation of Rhodamine B in aqueous solution. The mixed-phase TiO2 exhibits higher activity than pure phase TiO2, and the product containing 53.4% brookite and 46.6% anatase shows the highest photocatalytic activity. This behavior is explained by the mixed-phase effect between anatase and brookite. A proposed formation process is discussed to interpret the evolution of the phases based on the effects of different NaCl concentration and NH4OH/H2O volume ratio.