Lignin-derived carbon quantum dots-decorated Bi7O9I3 nanosheets with enhanced photocatalytic performance: Synergism of electron transfer acceleration and molecular oxygen activation

The design and development of high-efficient photocatalysts are confined by the limited light-harvesting capacity and rapid electron-hole recombination. The Bi7O9I3 nanosheets decorated by lignin-derived carbon quantum dots (CQDs) were prepared through a facile hydrothermal process, which was applied for the photocatalytic degradation of tetracycline hydrochloride (TC). The prepared CQDs/Bi7O9I3 composite with 3% CQDs content (CQDs/Bi7O9I3-3) showed the optimal photocatalytic degradation efficiency of 100% for TC under 300 W Xe lamp irradiation within 45 min. The corresponding degradation rate was 0.08133 min−1, which was 4.74 times higher than that of pure Bi7O9I3. The superoxide radicals (O2−) and holes (h+) were identified as the key reactive species for TC degradation through the photocatalytic mechanism exploration. The photocatalytic activity of CQDs/Bi7O9I3-3 composite could maintain above 80% after five recycles of degradation reaction, signifying its outstanding stability and reusability. The superior photocatalytic performance of CQDs/Bi7O9I3-3 is explained by the enhanced sunlight harvesting ability, accelerated electron transfer, and the formation of reactive species after the incorporation of CQDs. This work offers a promising strategy for constructing high-performance and environmentally friendly photocatalysts for water pollution treatment through the decoration of biomass-derived CQDs.