Fabrication of nitrogen doped graphene quantum dots-BiOI/MnNb2O6 p-n junction photocatalysts with enhanced visible light efficiency in photocatalytic degradation of antibiotics

Novel p-n junction photocatalysts nitrogen doped graphene quantum dots (NGQDs)-BiOI/MnNb2O6 have been prepared via hydrothermal method for the environmental remediation. The photocatalytic activity of as-prepared photocatalysts was evaluated by the degradation of different antibiotics such as tetracycline (TC), oxytetracyline, ciprofloxacin and doxycycline. Compared with single MnNb2O6 and BiOI, the hybrid materials (NGQDs-BiOI/MnNb2O6) could significantly enhance photocatalytic activity. Meanwhile, both the BiOI/MnNb2O6 ratio (Bi/Mn ratio) and the amount of NGQDs displayed important influence on the antibiotics degradation. In addition, the 5%NGQDs-Bi/Mn sample performed the optimum photo catalytic degradation toward TC (87.2%) within 60min. By further studies based on the electron spin resonance (ESR) and active species trapping experiments, this enhanced photocatalytic property could be ascribed to high charge carrier mobility of NGQDs and the p-n junction photocatalytic systems, which greatly promoted efficient separation of charge carriers. (C) 2016 Published by Elsevier B.V.