Bismuth-rich Bi4O5Br2 anchored on g-C3N4 nanosheets: Enhanced visible-light performance for simultaneous photocatalytic degradation of emerging pollutants and spectroscopic insights

Photocatalysis is gaining attention as a promising approach for completely degrading emerging pollutants (EPs); however, its capacity to degrade multiple EPs simultaneously remains largely underexplored. In this study, Bi4O5Br2/g-C3N4 composite heterojunction photocatalysts with varying g-C3N4 content were synthesized via a hydrolysis method followed by calcination. XRD analysis confirmed the monoclinic structure of Bi4O5Br2, while Helium ion microscopy (HIM) revealed a distinctive 3D flower-like hierarchical morphology. Elemental mapping by EDS and TEM studies verified the chemical purity and successful integration of Bi4O5Br2 with g-C3N4. The incorporation of 40 % g-C3N4 (BOB-40CN) resulted in enhanced visible-light absorption, evidenced by a red shift in the absorption edge, along with a reduction in bandgap energy. Among the prepared composites, BOB-40CN exhibited the highest photocatalytic activity, achieving 90 % degradation of acetaminophen (AC) under visiblelight irradiation within 50 min (rate constant: 0.043 min(-1)), in agreement with photoluminescence analysis. Additionally, photodegradation experiments on mixed solutions of AC and tetracycline (TC) in varying proportions demonstrated the capability of BOB-40CN to degrade both pollutants simultaneously. A plausible charge transfer mechanism was proposed based on the band structure of BOB-40CN and scavenger studies. Furthermore, time-resolved spectroscopy in the picosecond-to-nanosecond range confirmed the enhanced photocatalytic efficiency of BOB-40CN, attributed to reduced recombination losses at surface sites. Given the often-undetectable nature of EPs, it is imperative to focus on their simultaneous photodegradation, and this study is expected to inspire researchers to develop novel photocatalysts for this purpose.