Enhanced full solar spectrum photocatalysis by nitrogen-doped graphene quantum dots decorated BiO2-x nanosheets: Ultrafast charge transfer and molecular oxygen activation

It is still challenging to produce superoxide and hydroxyl radicals through activating molecular oxygen under broad-spectrum light in environmental photocatalysis. In this work, nitrogen-doped graphene quantum dots (N-GQDs) modified BiO2-x nanosheets were successfully fabricated and exhibited superior performance in light-harvesting, electron-hole pair separation, and full-spectrum driven molecular oxygen activation. The hybridized photocatalyst with a N-GQDs weight ratio of 0.4wt% (GBO-0.4) exhibited an excellent photocatalytic activity toward tetracycline degradation with a 4.0-fold, 2.9-fold and 5.5-fold higher reaction rate under full-spectrum, visible and near-infrared light irradiations than that of pure BiO2-x, respectively. The enhanced photocatalytic performance was ascribed to the electron collection effect and up-conversion photoluminescence properties of the N-GQDs as well as the synergistic effects of the developed nanojunction. Efficient molecular oxygen activation was achieved via the construction of a bulk-to-surface channel between BiO2-x and N-GQDs. DFT calculations were also used to explore the geometric and electronic structure variations of BiO2-x after the introduction of N-GQDs. The high photostability and mineralization ability toward tetracycline degradation confirm the promising application prospects of the N-GQDs/BiO2-x photocatalyst. This work provides a rational strategy for designing 0D/2D nanoscale heterostructure photocatalysts with improved full-spectrum photoactivity for environmental applications.