Room‐Temperature Hydrolysis of Potassium Titanyl Oxalate and Water‐Assisted Crystallization for TiO2 with High Photocatalytic Activity

The commonly adopted approach to synthesize nanostructured TiO2 starting from titanates demands a hydrothermal environment to achieve the titanate precursor, and a subsequent high temperature calcination to fulfill the decomposition of titanates and crystallization of TiO2. In this report, hydrogen titanate aggregates were achieved by a room-temperature hydrolysis of a potassium titanyl oxalate in an aqueous H2O2 solution. The subsequent immersion in water at 80 °C induced the crystallization of TiO2 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 m2/g) and pore volume (∼0.50 cm3/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 TiO2 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).