0D Bi nanodots/2D Bi3NbO7 nanosheets heterojunctions for efficient visible light photocatalytic degradation of antibiotics: Enhanced molecular oxygen activation and mechanism insight

Solar-driven molecular oxygen activation is a promising and low energy-cost way for environmental remediation. To fabricate semimetal/semiconductor composite photocatalyst is an effective strategy to accelerate the transfer and separation of photogenerated carriers for boosting molecular oxygen activation. Herein, we report a 0D Bi nanodots/2D Bi3NbO7 nanosheets heterostructured composite with enhanced molecular oxygen activation under visible light irradiation, which was synthesized by a two-step wet chemical method. Transmission electron microscopy (TEM) analysis shows that the Bi nanodots with diameters of 2-5 nm were uniformly distributed on the surface of Bi3NbO7 nanosheets. More importantly, both experiments and density functional theory (DFT) calculations confirm that a strong covalent interaction existed between the Bi atom of Bi nanodots and Bi-O layer on the surface of the Bi3NbO7 nanosheets, which enhanced the visible light absorbability of the composite, fostered the transfer and separation of its interfacial photogenerated carriers, and promoted the activation of molecular oxygen into superoxide radicals (center dot O-2(-)) and singlet oxygen (O-1(2)) by the composite under visible light illumination for degradation of ciprofloxacin (CIP). The photocatalytic degradation rate of CIP by the Bi/ Bi3NbO7 composites is 4.58 times higher than that by the pristine Bi3NbO7. The Bi/Bi3NbO7 photocatalyst still revealed high photocatalytic activity even after five cycles. This work elucidates the mechanism of molecular oxygen activation over 0D/2D semimetal-semiconductor system and provides a promising approach for designing high efficient 0D/2D photocatalysts toward sustainable environmental remediation.