Enhanced visible light photocatalytic degradation of dyes by the oxygen-rich vacancy-assisted S-scheme heterojunction Al 2 O 3 /BiOBr: Catalytic mechanism and performance evaluation

A heterojunction Al 2 O 3 /BiOBr composite photocatalyst, characterized by an S -scheme structure and enriched with oxygen vacancies, was synthesized through a solvothermal reaction coupled with an in situ growth approach. Oxygen vacancies on the catalyst surface, enhanced by the robust coupling between Al 2 O 3 and BiOBr, were corroborated by X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR). Techniques such as UV - vis diffuse reflectance spectroscopy (DRS), UV photoelectron spectroscopy (UPS), Mott - Schottky characterization, and experimental radical trapping experiments collectively validated the pathways for migrating photogenerated carriers. The interplay between the surface oxygen vacancies and the Sscheme Al 2 O 3 /BiOBr heterojunction, which possesses potent redox capabilities, significantly improved the photocatalytic degradation. This enhancement was particularly evident in the outstanding visible photocatalytic degradation performance against rhodamine B (RhB), methyl orange (MO), and basic fuchsin (BF). The synthesized composite photocatalysts demonstrated 92% retention of degradation efficiency after five recycling cycles, indicating their considerable stability.