Unveiling the Role of Defects on Oxygen Activation and Photodegradation of Organic Pollutants

The status of defects of TiO 2 are of fundamental importance in determining its physicochemical properties. Here we report a simple chemical deposition method for controllable synthesis of defective anatase TiO 2 nanocrystals under various calcination atmospheres. XPS and ESR analysis reveals that both the oxygen vacancies ( V O ) and the trivalent titanium (Ti 3+ ) defects exist in TiO 2 after N 2 treatment (N-TiO 2 ). Meanwhile, mainly V O defects can be obtained in TiO 2 with air calcination (A-TiO 2 ). ESR spectra for reactive oxygen species determination, clearly show that the visible light catalytic activity is mainly caused by the efficient activation of oxygen molecules to •O 2– species for A-TiO 2, which play an important role in hindering the accumulation of intermediates during p -chlorophenol (4-CP) photodegradation process. However, the oxygen molecules cannot be activated for N-TiO 2 even with superior visible light absorption and thus the photogenerated electron are reductant, which participated in the transformation of BQ to HQ via electron shuttle mechanism. Moreover, A-TiO 2 exhibits higher separation efficiency of photogenerated carriers than that of N-TiO 2, showing the critical role of V O with a suitable concentration in transferring photogenerated charges.