Preparation of thermally stable anatase TiO2 photocatalyst from TiOF2 precursor and its photocatalytic activity

Preparation of anatase TiO2 with high themal stability is of great importance for its environmental application. In this work, TiOF2 was first synthesized by a simple microwave-assisted hydrothermal route using tetrabutyl titanate and hydrofluoric acid as precursors at 200 degrees C for 20 min. Then the resulted precipitates were calcined at different temperatures (300-1000 degrees C) for 2 h. The as-prepared samples were characterized by X-ray diffraction, Raman spectrum, scanning electron microscopy, N-2 adsorption-desorption isotherms and X-ray photoelectron spectroscopy. The photocatalytic activity was evaluated using Brilliant Red X3B, an anionic azo dye, as the target organic molecule under UV light irradiation. The results showed that the prepared TiOF2 exhibited weak or no photocatalytic activity. The phase transformation of TiOF2 to anatase TiO2 occurred at about 300 degrees C. The prepared anatase TiO2 from TiOF2 showed very high thermal stability and the anatase-to-rutile phase transformation temperature was up to 1000 degrees C. Fluoride ions played an important role in the improvement of thermal stability of anatase TiO2 by strongly adsorbing on the crystal planes of anatase to stabilize the anatase structure. The 700 degrees C-calcined sample showed the highest photocatalytic activity due to its relative good crystallization and high specific surface areas. (c) 2011 Elsevier B.V. All rights reserved.