Room-Temperature Hydrolysis of Potassium Titanyl Oxalate and Water-Assisted Crystallization for TiO_2 with High Photocatalytic Activity

摘要

The commonly adopted approach to synthesize nanostructured TiO_2 starting from titanates demands a hydrothermal environ- ment to achieve the titanate precursor, and a subsequent high temperature calcination to fulfill the decomposition of titanates and crystallization of TiO_2. In this report, hydrogen titanate aggregates were achieved by a room-temperature hydrolysis of a potassium titanyl oxalate in an aqueous H_2O_2 solution. The subsequent immersion in water at 80 ℃ induced the crystal- lization of TiO_2 with a mixture of anatase nanoparticles and rutile nanorods. The anatase fraction increased with increasing immersing duration in hot water for up to 72 h. The low- temperature crystallized TiO2 powders possessed abundant surface hydroxyl groups (~38%), high specific surface area (~ 126 m~2 /g) and pore volume (~0.50 cm~3 /g). When utilized to assist photodegradation of rhodamine B in water under UV light illumination, the reaction rate constant was twice that of the commercial P25 TiO_2 nanoparticles. The high photocatalytic activity is contributed to the abundant surface hydroxyl groups, high specific surface area, and the appropriate mixture of anatase nanoparticles and rutile nanorods (~84:16 in weight).