Simple preparation of sub-micron mesoporous TiO2 spheres consisting of anatase nanocrystals

Mesoporous anatase titania spheres with an average size of approx. 400 nm were facilely prepared at low temperature by treating the titanium glycolate precursor spheres with hot water (∼100 °C). The surface of the precursor particle became rough and the anatase phase began to form when it was treated with hot water for 1.5 h. With increasing treatment time, the crystallinity of the particles was improved, and the nanoporous structure further formed in the interior of the spheres. When the treatment time was prolonged to 6 h, the mesoporous anatase spheres were finally obtained, and they were composed of interconnected nanocrystals with the size less than 15 nm and pores with the mean size of 8.31 nm. The as-prepared mesoporous anatase titania spheres exhibited excellent adsorption capacity and better photocatalytic activity compared with the commercial photocatalyst P-25 due to the large specific surface area. Ostwald ripening and surface energy effects were presumed to play an important role in the formation of mesoporous structure and anatase nanocrystals.