A facile solid phase reaction to prepare TiO2 mesocrystals with exposed {001} facets and high photocatalytic activity

As one of the most widely investigated and used materials, TiO2 is expected to play a leading role in helping solve environmental and energy issues. In this work, we developed a facile, greener and more controllable approach of preparing anatase TiO2 mesocrystals with largely exposed {001} facets. This approach utilizes the solid-solid topotactic transformation of NH4TiOF3 to anatase TiO2 and only needs a simple sintering process. In order to obtain the exposed {001} facets on the surfaces of final products, the sintering temperature must be between 700 degrees C and 900 degrees C. Temperatures below 700 degrees C lead to unexposed {001} facets. Temperatures above 900 degrees C lead to a mixed phase of anatase and rutile. The photocatalytic activity of the TiO2 mesocrystals is much higher than that of the corresponding TiO2 polycrystalline materials and comparable with that of commercially available P25. The exposed {001} facets are believed to play a very important role in the photocatalysis process.