Chemically bonded carbon quantum dots/Bi2WO6 S-scheme heterojunction for boosted photocatalytic antibiotic degradation: Interfacial engineering and mechanism insight

Design of green and low-cost S-scheme heterojunctions with strong interface interactions is critical to their photocatalytic performance and practical application. Here, novel S-scheme heterojunctions of 0D/2D carbon quantum dots/Bi2WO6 (CQDs/Bi2WO6) were successfully fabricated by an in-situ hydrothermal process, where the CQDs were derived from waste biomass. The Bi-O-C bonds were formed at their interface, providing an atomic-level interfacial channel for promoting charge separation. As supported by work function calculations, in-situ X-ray photoelectron spectroscopy (XPS), and electron paramagnetic resonance (EPR) analyses, an S-scheme charge migration path was unveiled within the CQDs/Bi2WO6 during the photocatalytic reaction. The 3 wt%CQDs/Bi2WO6 S-scheme heterojunction displayed an optimal photocatalytic activity, which is 4.01 and 64.71 times higher than those of Bi2WO6 and CQDs, respectively. Based on theoretical calculations and experimental results, the photocatalytic mechanism, possible intermediates, and degradation pathways were enunciated. Furthermore, the non-toxicity of the developed heterojunction and degraded tetracycline solution was testified by E.coli cultivation.