Defective TiO_2 prepared via synchronous crystallization and constraint reduction strategy with enhanced photocatalytic activity

摘要

Defects (oxygen vacancy and Ti~(3+)) play crucial roles in determining band structure, light absorption, and catalytic activity of TiO_2. Herein, a synchronous crystallization and constraint reduction strategy was reported to construct controllable defective TiO_2 using sodium borohydride (NaBH_4) as the reductant. The constraint decomposition effect of NaBH_4 in pore channels of TiO_2 aerogels enables the defects migrate from surface to bulk region effectively, and bulk defects are more stable. Moreover, the species and concentration of defects can be controlled by changing the calcination temperature in this case. An optimum temperature for the NaBH_4 treatment was found to be 500 °C. After the reduction at 500 °C, defective TiO_2 with maximum bulk oxygen vacancies shows excellent visible light absorption performance, effective separation of photogenerated charge carriers, and suitable band edge, and the removal rate was 94.9% for rhodamine B (RhB) under visible light which was about 325% higher than that of TiO_2 without oxygen vacancy.