Photocatalytic Properties of Nanocrystalline TiO2 Synthesized by Highpressure Microwave Method

Nanocrystalline TiO2 powders were synthesized from TiCl4 solution by the highpressure microwave method under pressure ranging from 0.1MPa to 4.0MPa. The phase structures, microstructures and photocatalytic properties of the nanocrystalline TiO2 were investigated. It was found that the reaction pressure had a large impact on the phase structures, microstructures, and photocatalytic properties of the nanocrystalline TiO2. Under lower reaction pressure, TiO2 products consisted of anatase and brookite phase, with the brookite phase in minority, while under higher reaction pressure, a large quantity of rutile TiO2 was formed. With the increase of reaction pressure from 0.1MPa to 4.0MPa, the average sizes of the TiO2 nanoparticles increased from 5nm to 30nm. At reaction pressures lower than 2.0MPa, the photocatalytic performance of the nanocrystalline TiO2 increased with the pressure, while at pressures higher than 2.0MPa, the photocatalytic performance was found to decrease monotonically with the pressure.