Up-converted nitrogen-doped carbon quantum dots to accelerate charge transfer of dibismuth tetraoxide for enhanced full-spectrum photocatalytic activity

The charge carriers' separation and the light harvesting ability are two key factors affecting the photocatalytic activity of photocatalysts. In this work, nitrogen-doped carbon quantum dots (N-CQDs) modified Bi2O4 (N-CQDs/Bi2O4) are fabricated via a facile hydrothermal method, which serve as efficient photocatalysts toward methyl orange (MO) degradation. The photocatalytic experimental results demonstrate that enhanced photocatalytic activities are acquired for all N-CQDs modified Bi2O4 composites. Moreover, 0.3 % N-CQDs/Bi2O4 exhibits the optimal photocatalytic activity with the reaction rate about 3.1-fold, 2.3-fold, and 2.9-fold of pure Bi2O4 under solar light, visible light, and near-infrared light irradiation. Such significantly increased photocatalytic performance can be ascribed to the following two advantages of N-CQDs: high conductivity that accelerate the separation of charge carriers and the upconversion behavior to enlarge light harvesting range. Additionally, the trapping experiments suggest that holes (h(+)) are of vital importance for the degradation process. This work paves the way for developing advanced photocatalyst with high charge separation efficiency and full-spectrum utilization.