Photocatalytic properties of mesoporous TiO₂ prepared by hydrothermal method

Mesoporous TiO₂ was synthesized by hydrothermal treatment of titanic acid hydrate (H₂Ti₂O₅.XH₂O) from potassium titanate (K₂Ti₂O₅) via ion-exchange and glucose in aqueous solution at 220°C, followed by a posttreatment in the presence of air at 520°C The photocatalyst was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), N₂ adsorption, and transmission electron microscopy (TEM). Results indicated that the prepared mesoporous TiO₂ photocatalyst was micron-sized rod or needle morphology and had a mesoporous structure with a surface area of 106m².g^-1, pore volume of 0.31 cm ³.g^-1, and a pore diameter of 8.06 nm. The crystal size was 12.3 nm. After calcination it was still anatase phase. The produced carbon considerably increased the thermal stability of the mesoporous TiO₂ framework and inhibited undesirable grain growth as well as phase transformation during the hydrothermal and thermal treatment process. Photocatalytic degradation performance was investigated using methyl orange pollutant. The mesoporous TiO₂ photocatalyst and Degussa P25 showed similar degradation behavior toward methyl orange. The mesoporous TiO₂ could be recycled many times and this was because of the large grain size. Using KI as a probe reaction, we found that the photocatalytic mechanism of mesoporous TiO₂ depended on photoinduced hole oxidation.