Direct Sonochemical Preparation and Characterization of Highly Active Mesoporous TiO<INF>2</INF> with a Bicrystalline Framework

In this study mesoporous TiO<INF>2</INF> with a bicrystalline (anatase and brookite) framework was synthesized directly under high-intensity ultrasound irradiation. This was carried out separately, both with and without the use of a triblock copolymer. Without thermal treatment, mesoporous TiO<INF>2</INF> was formed by the agglomeration of monodispersed TiO<INF>2</INF> sol particles. The resulting materials were characterized by XRD, TEM, nitrogen adsorption, TGA/DTA, and FTIR. The use of ultrasound irradiation assisted in the formation of the brookite phase. As the content of the brookite phase increased, the pore size and the crystalline sizes of anatase and brookite became larger when the triblock copolymer was used in the synthesis. Both as-prepared samples exhibited better activities than the commercial photocatalyst P25 in the degradation of n-pentane in air. The degradation rate of mesoporous TiO<INF>2</INF> synthesized in the presence of triblock copolymer was about two times greater than that of P25. The high activities of the mesoporous TiO<INF>2</INF> with a bicrystalline framework can be attributed to the combined effect of three factors:  high brookite content, high surface area, and the existence of mesopores.