Enhancing effects of water content and ultrasonic irradiation on the photocatalytic activity of nano-sized TiO2 powders

A simple method for preparing highly photoactive nano-sized TiO2 photocatalyst with anatase and brookite phase was developed by hydrolysis of titanium tetraisopropoxide in pure water or the EtOH/H2O mixed solution under ultrasonic irradiation. The prepared TiO2 powders were characterized by differential thermal analysis (DTA), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and BET surface areas. The photocatalytic activity was evaluated by the photocatalytic oxidation of acetone in air. The results showed that the photocatalytic activity of TiO2 powders prepared by this method from pure water or the EtOH/H2O mixed solutions with the molar ratio of EtOH/H2O = I exceeded that of Degussa P-25. The molar ratios of EtOH/H2O obviously influenced the crystallization, crystallite size, BET surface areas and photocatalytic activity of the prepared TiO2 powders. Ultrasonic irradiation obviously enhanced the photocatalytic activity of TiO2 powders whether the solvent is pure water or the EtOH/H2O mixed solutions. This may be ascribed to the fact that ultrasonic irradiation enhances hydrolysis of titanium alkoxide and crystallization of TiO2 gel. (C) 2002 Elsevier Science B.V. All rights reserved.