S-scheme BiOBr/Bi2WO6 with oxygen vacancies for synergistic photodegradation and hydrogen generation: Mechanisms insight and DFT calculations

Abstract

An S-type heterojunction photocatalyst Bi2WO6/BiOBr (BWO/BiOBr) with an interlaced band structure and abundant oxygen vacancies (Ov) was synthesized using a hydrothermal method and high-temperature calcination. The surface was modified with carbon quantum dots (CQDs) to create a 0D/2D/2D structure. The resulting photocatalyst exhibited superior performance, with a degradation rate for Norfloxacin (NOR) antibiotics surpassing Bi2WO6 with oxygen vacancies (BWO-Ov) and BiOBr by 6.55 and 3.96 times, respectively. Notably, it achieved a high hydrogen generation rate of 459.49 μmol·g−1·h−1 under visible light. The enhanced carrier transfer and solar absorption were attributed to the synergistic effect of CQDs and S-type heterojunctions. The face-to-face 2D/2D structure provided abundant reaction sites. The influence of initial NOR concentration and photocatalyst dosage on photocatalytic activity was investigated in our study. Incorporating CQDs improved solar absorption, as confirmed by NOR degradation under various wavelengths. Electron spin resonance (ESR) analysis indicated the generation of reactive oxygen species. Density functional theory (DFT) calculations and characterization explored charge transfer mechanisms and degradation pathways. These findings contribute to the design of efficient S-type heterogeneous photocatalysts for sustainable energy and environmental applications.