Template-free fabrication of rattle-type TiO2 hollow microspheres with superior photocatalytic performance

Abstract

In the paper, an environmentally friendly and template-free route based on a simple hydrothermal process has been developed for preparing rattle-type TiO₂ hollow microspheres by using titanium(IV) sulfate (Ti(SO₄)₂) as the titanium source and glycerol/water as the cosolvent. The SEM and TEM images showed that the obtained TiO₂ products were rattle-type hollow nanostructures with a diameter of ca. 1.1 μm. More importantly, the products have a good thermal stability and high crystallinity, which is favorable for their practical applications. According to the experimental results, a possible formation mechanism involving the Ostwald ripening process was proposed combined with various techniques such as SEM, TEM, BET, IR, and UV-vis. The photocatalytic results indicated that the TiO₂ microspheres obtained from 750 °C thermal treatment exhibited higher photocatalytic activity for the photodegradation of methyl orange (MO) than those of other calcination temperatures and commercial Degussa P25. To further improve the photocatalytic activity, Ag-doped TiO₂ photocatalyst was also prepared by the impregnation method. The results indicated that the photocatalytic activity of the Ag/TiO₂ catalysts was greatly enhanced compared with the pure TiO₂ catalysts. The possible photodegradation mechanism was also discussed.