Novel 2D/3D BiOBr/TiO2 S-scheme heterostructures photocatalyst fabrication for remarkable ciprofloxacin degradation under solar light

Abstract

The creation of sophisticated S-scheme heterojunction photocatalysts presents a pioneering approach to enhance pollutant degradation through improved charge separation and light absorption. This study introduces a novel 2D/3D BiOBr/TiO₂ S-scheme heterojunction photocatalyst designed to elevate the degradation efficiency of ciprofloxacin (CIP), an antibiotic contaminant, when exposed to natural sunlight. Characterization of the structure and morphology confirmed the successful integration of BiOBr nanosheets onto TiO₂ nanoparticles, resulting in an optimized heterostructure. Both TiO₂ and the BiOBr-modified TiO₂ (BiOBr/TiO₂) were synthesized using a facile hydrothermal method followed by a slow evaporation process. The BiOBr/TiO₂ composite exhibited significantly enhanced visible-light absorption compared to pure TiO₂, attributed to the light-absorbing properties of BiOBr and the effective formation of the S-scheme heterojunction. This configuration facilitated efficient charge separation, as demonstrated by photoluminescence (PL) quenching and decreased charge-transfer resistance observed in electrochemical impedance spectroscopy (EIS) analyses. The S-scheme mechanism enabled selective recombination of low-energy charge carriers while retaining high-energy electrons and holes, thus maximizing redox potential. Under sunlight irradiation, the BiOBr/TiO₂ composite achieved an impressive 93 % photocatalytic degradation of CIP, significantly outperforming both standalone TiO₂ and BiOBr. Trapping experiments highlighted the crucial roles of hydroxyl radicals (•OH⁻) and superoxide radicals (•O₂⁻) as reactive species driving the degradation process. This research underscores the substantial potential of S-scheme heterojunction photocatalysts for advanced wastewater treatment applications, offering a sustainable and effective solution to environmental remediation challenges.