Tunable oxygen activation induced by oxygen defects in nitrogen doped carbon quantum dots for sustainable boosting photocatalysis

Nitrogen-doped carbon quantum dots (N-CQDs)/BiPah materials have been prepared through an ionic liquid assisted solvothermal method. After the introduction of N-CQDs, the N-CQDs/BiPO4 materials exhibited the increased photocatalytic activity for the degradation of four kinds of colorless pollutants under UV irradiation, such as antibiotic ciprofloxacin, enrofloxacin, tetracycline and phenol 4-chlorophenol. Different from roles of carbon quantum dots previous reported, the improved photo catalytic activity was mainly attributed to the molecular oxygen activation ability of N-CQDs, which derived from the oxygen defects on the surface of N-CQDs. The N-CQDs/BiPO4 materials displayed excellent reusability and stability and demonstrated the oxygen defects in N-CQDs could sustainable activate molecular oxygen for organic pollutant removal under UV irradiation. By the electron spin resonance analysis, the main active species was determined to be superoxide radicals rather than hydroxyl radicals. This study presented some new insight for the mode of action of N-CQDs for the increased photocatalytic activity and also provided an approach to enhance the molecular oxygen activation for photocatalytic pollutant removal or selective organic synthesis. (C) 2016 Elsevier Ltd. All rights reserved.