Activation of molecular oxygen in selectively photocatalytic organic conversion upon defective TiO2 nanosheets with boosted separation of charge carriers

Abstract

Defects play a pivotal role in not only the separation of electrons and holes in photocatalysis but also the activation of molecular oxygen in selective photocatalysis. Herein, defect distribution of TiO2 nanosheets was regulated via annealing the pristine TiO2 sample in oxygen and hydrogen atmospheres successively. The results show that the combination of suitable distribution of oxygen vacancy (VO) promotes the separation of charge carriers, improving the photocatalytic hydrogen evolution. More interestingly, VOs boost the activation of molecular oxygen to singlet oxygen (1O2) and superoxide anion radical (•O2–) in selectively photocatalytic oxidation of benzylamine to imine. Generation of 1O2 and •O2– is a competitive process, which can be regulated via adjusting the distribution of oxygen defects, and the key species is 1O2 that can be mainly induced by VOs. These results can provide an avenue to the defect engineering upon photocatalysts used to selective organic synthesis.