Engineering an S-scheme Bi2O2S/boron nitride heterojunction with dual-channel charge transfer for superior photocatalytic degradation of carbamazepine

Bi 2 O 2 S/BN heterojunction: carbamazepine (CBZ) photodegradation. • Built-in electric field promotes spatial charge separation and migration. • Dual •OH/O 2 •− channels selectively attack distinct reactive sites in CBZ. • Bi 2 O 2 S/BN removes 93.4% of CBZ with a 4.7-fold rate enhancement. • Catalyst remains robust in real waters and reduces overall toxicity. The persistent and ecotoxic pharmaceutical carbamazepine (CBZ) poses a significant threat to aquatic environments. Although semiconductor photocatalysis offers a green solution, its efficiency is often hindered by rapid charge recombination and limited light absorption. In this study, we reported the rational design and construction of an S-scheme dibismuth oxysulfide/boron nitride (Bi 2 O 2 S/BN) heterojunction through intimate interfacial coupling between Bi 2 O 2 S and BN. This strategic integration induced strong interfacial electron coupling, resulting in a built-in electric field that regulated interfacial band bending and facilitated spatial charge separation of photogenerated electron-hole pairs, as unequivocally validated by experimental characterizations and density functional theory (DFT) calculations. The optimized Bi 2 O 2 S/BN heterojunction achieved 93.4% ± 0.1% CBZ removal within 120 min, with an apparent rate constant of 0.0155 ± 0.0001 min −1 , representing a 4.7-fold enhancement over pristine Bi 2 O 2 S. Notably, beyond conventional activity improvement, this system established spatially partitioned redox sites via work-function-driven charge redistribution, enabling a dual-channel oxidative pathway that selectively targeted distinct electrophilic and nucleophilic sites of the CBZ molecule. This molecular-level reaction matching distinguished the proposed system from previously reported CBZ photocatalysts, which primarily relied on indiscriminate reactive oxygen species (ROS) oxidation. This study reports a highly effective and stable photocatalyst for remediating persistent pollutants. Additionally, it provides mechanistic insights into interfacial charge regulation and charge-transfer dynamics in heterojunction systems, offering a valuable blueprint for designing advanced photocatalytic systems for practical environmental applications. Download: Download high-res image (404KB) Download: Download full-size image