Cocatalyst CQDs Induce Morphology Evolution and Interfacial Electron Transfer in Bi ₂ WO ₆ for Superior Photocatalytic Degradation

The development of efficient photocatalysts is crucial for addressing water pollution caused by organic contaminants. This study adopted a cocatalyst modification strategy to successfully prepare carbon quantum dots-modified bismuth tungstate (CQDs/Bi 2 WO 6 ) composite photocatalysts. The introduction of CQDs induced the transformation of Bi 2 WO 6 from isolated nanosheets into a hierarchical flower-like architecture, which increased the specific surface area and provided abundant active sites. Using rhodamine B, methylene blue, and tetracycline hydrochloride as target pollutants, the visible-light photocatalytic degradation performance of the composites was systematically investigated. The results showed that the optimal sample CQDs/Bi 2 WO 6 -1 exhibited superior activity, achieving 96.3%, 92.0%, and 47.2% degradation of rhodamine B, methylene blue, and tetracycline hydrochloride within 50 min, respectively, with good stability after four reuse cycles. Mechanism investigations, including radical trapping experiments and electron spin resonance spectroscopy, identified ·O 2 – and ·OH radicals as the primary reactive species. Furthermore, liquid chromatography–mass spectrometry analysis of degradation intermediates, complemented by density functional theory calculations, elucidated an interfacial electron transfer pathway from Bi 2 WO 6 to CQDs. The successful preparation of this material effectively suppresses charge recombination and increases the number of active sites, which accounts for its superior photocatalytic performance. This research presents an innovative strategy for designing efficient photocatalytic materials, offering both important theoretical insights and promising practical application prospects in the field of organic pollutant treatment.