AgBr-garlic peel QD system: a promising composite for simultaneous degradation of a binary mixture of cationic and anionic dyes

Abstract

The conversion of waste into value-added products is a key focus of modern research. In this study, we synthesized nitrogen (N) and sulfur (S) co-doped carbon quantum dots (CQDs) from garlic peel using a hydrothermal method and incorporated them into silver bromide (AgBr) to enhance the photocatalytic efficiency. The AgBr–QD composite was prepared with QD concentrations of 1, 5, 10, 20, and 30 wt%, and the 20 wt% QD composite exhibited the highest photocatalytic activity. Under visible light irradiation, this optimized composite achieved 92.4% degradation of a dye-contaminant mixture within 15 minutes. The improved performance was attributed to enhanced charge separation and reduced electron–hole recombination, as confirmed by radical trapping experiments, which identified holes as the primary active species in the photodegradation. These findings suggest that garlic peel-derived QDs can significantly enhance the efficiency of AgBr-based photocatalysts for wastewater treatment.