Effects of urea on the microstructure and photocatalytic activity of bimodal mesoporous titania microspheres

Abstract: Bimodal mesoporous TiO2 microspheres with high photocatalytic activity were prepared by a hydrothermal method using titanium sulfate as precursor in the presence of urea. The results indicate that all prepared samples show bimodal pore-size distributions in the mesoporous region: smaller intra-aggregated pores with peak pore diameter of ca. 2nm and larger inter-aggregated pores with peak pore diameter of ca. 12.5nm. The molar ratio of urea to Ti(SO4)2 (R u) has an obvious influence on the morphology, microstructure and photocatalytic activity of TiO2. With increasing R u, specific surface areas and porosity increase, contrarily, the crystallite size and relative anatase crystallinity decrease. The photocatalytic activity first increases with R u. At R u =2.0, the photocatalytic activity reaches the highest and is obviously higher than that of Degussa P25. With further increasing R u, the photocatalytic activity decreases. The formation rate of hydroxyl radicals during photocatalysis has a positive correlation with the photocatalytic activity. [Copyright &y& Elsevier]