Particle size of nanomaterials has significant impact on their photocatalyst properties. In this paper, TiO2 nanoparticles with different crystalline sizes were prepared by adjusting the alkali-hydrothermal time (0-48 h). An annealing in N2 atmosphere after hydrothermal treatment caused TiO2 reduction and created defects, resulting in the visible light photocatalytic activity. The evolution of physicochemical properties along with the increase of hydrothermal time at a low alkali concentration has been revealed. Compared with other TiO2 samples, TiO2-24 showed higher photocatalytic activity toward degrading Rhodamine B and Sulfadiazine under visible light. The radical trapping and ESR experiments revealed that O2•- is the main reactive specie in TiO2-24. Large specific surface areas and rapid transfer of photogenerated electrons are responsible for enhancing photocatalytic activity. The above findings clearly demonstrate that particle size and surface oxygen defects can be regulated by alkali-hydrothermal method. This research will deepen the understanding of particle size on the nanomaterials performance and provide new ideas for designing efficient photocatalysts.
Keywords: TiO2; alkali; particle size; photocatalysis; surface oxygen defects.