Carbon Quantum Dot-Decorated BiOBr/Bi2WO6 Photocatalytic Micromotor for Environmental Remediation and DFT Calculation

Efficient photocatalysts are crucial for degrading antibiotic pollutants in water and vital for environmental remediation. In this study, an efficient carbon quantum dot (CQD)-modified BiOBr/Bi2WO6 hybrid material was prepared by a mild hydrothermal method. Meanwhile, a visible-light-driven micromotor based on the photocatalyst was developed. The micromotor can achieve self-propelled motion powered by the photocatalytic degradation reaction. It exhibited remarkable photocatalytic activity toward common pollutants in water, such as sulfonamide, quinolone, and tetracycline antibiotics. Among them, 10CQD/BiOBr/Bi2WO6-4 (10CBBr-4) exhibited the highest photocatalytic activity, which was 2.8 and 5 times higher than those of BiOBr and Bi2WO6, respectively. The high activity is attributed to the decoration of CQDs, which promoted visible-light absorption. Additional contributions may be due to the specific Z-type electron transport mode and flower-like BiOBr inserted by two-dimensional (2D) Bi2WO6 nanosheets, which enriched the active reaction sites, facilitated the adsorption of antibiotic molecules, and promoted the final radical attack. Based on the theoretical calculation of molecular orbitals and the Fukui index, the possible intermediate products, degradation pathways, and photocatalytic mechanism were elucidated. This study suggests that structural engineering based on CQD modification effectively allows the design of self-propelled microrobots for antibiotic degradation.