Controlled charge transfer in well-structured Cs 3 Bi 2 Br 9 @TiO 2 heterojunctions for enhanced visible-light photocatalytic degradation of tetracycline hydrochloride

The efficient removal of antibiotic residues has become a significant concern, yet it remains a considerable challenge. Constructing heterojunctions with enhanced interfacial charge transfer represents a promising approach for improving photocatalytic efficiency. In this study, lead-free perovskite Cs₃Bi₂Br₉ quantum dots were combined with TiO₂ through a hydrolysis-calcination route to fabricate a core-shell Cs₃Bi₂Br₉@TiO₂ nanocomposite. Detailed characterization verified the successful formation of a well-defined type-II heterojunction with strong and intimate contact at the component interface. The nanocomposite showed enhanced visible-light absorption and favorable band alignment, promoting efficient separation and transfer of photogenerated charge carriers. In photocatalytic tests for tetracycline hydrochloride degradation, the nanocomposite outperformed pristine Cs₃Bi₂Br₉ across various light sources, attaining a degradation efficiency of 92.76% under 450 nm irradiation. This study highlights the potential of lead-free perovskite-based heterojunctions in developing efficient and environmentally friendly photocatalysts for pollutant degradation.