Construction of 3D marigold-like Bi₂WO₆/Ag₂O/CQDs heterostructure with superior visible-light active photocatalytic activity toward tetracycline degradation and selective oxidation

A novel visible-light-driven photocatalyst Bi₂WO₆/Ag₂O/CQDs (BWO/Ag₂O/CQDs), which possesses hierarchical superstructure with marigold-like appearance, was fabricated via a hydrothermal method, followed by a simple precipitation process. Ag₂O nanoparticles sized around 25 nm and CQDs with diameters of about 10 nm were evenly deposited on Bi₂WO₆ to form a unique heterostructure. The obtained BWO/Ag₂O/CQDs heterostructure showed excellent adsorption and remarkably enhanced photocatalytic performance in the photodegradation of antibiotic tetracycline (TC) under visible-light irradiation compared to pristine Bi₂WO₆. The degradation rate of TC over BWO/Ag₂O/CQDs photocatalyst is 16.2 times higher than that of pristine Bi₂WO₆ and a possible mechanism for the enhanced photocatalytic performance was discussed. In addition, BWO/Ag₂O/CQDs was applied in the selective oxidation of benzyl alcohol to benzaldehyde under visible-light illumination. The result demonstrated that the conversion rate and product selectivity are greatly improved over BWO/Ag₂O/CQDs compared to pristine Bi₂WO₆ in the same reaction conditions, making it a promising photocatalyst in the application of green chemical transformation. The co-coupling of CQDs and Ag₂O with matched band potentials gives a substantial promotion for the light harvesting ability and effective separation of photogenerated charge carriers, synergistically accounting for the improvement of photocatalytic efficiency.