Simulated sunlight-enhanced peroxymonosulfate activation via S-scheme BiOBr/g-C3N4 aerogel heterojunction for multi-pollutant remediation: Band structure and interface engineering

The intricate composition of real-world aquatic systems significantly constrains the improved overall performance of powder catalysts, meanwhile their recyclability is inferior to the bulk counterparts (e.g. aerogels). Herein, by loading BiOBr onto g-C₃N₄ nanosheets and combining them with agarose, an S-scheme heterojunction aerogel (abbreviated as BCA) was synthesized, whose structure was confirmed by the density functional theory calculation. Importantly, the BCA could activate peroxymonosulfate (PMS) under simulated sunlight for degrading multi-pollutant. And the BCA/PMS/Light system efficiently degraded various organic contaminants in aqueous environments, achieving a high degradation rate constant of 0.1503 min⁻¹ for rhodamine B (RhB), significantly surpassing the performance of CA/PMS/Light (0.0378 min⁻¹) and BCA/PMS (0.0763 min⁻¹) systems. Free radical quenching experiment and electron paramagnetic resonance analysis reveal that ¹O₂, •O₂^–, •OH and SO₄•⁻ in the BCA/PMS/Light system were pivotal in RhB degradation, with a dominant non-radical mechanism. Additionally, Fukui function analysis pinpointed the primary reaction sites within the RhB molecule. The photocatalytic heterojunction aerogel exhibits outstanding stability, environmental sustainability and versatility, which can guide the development of simulated sunlight-driven PMS activation for multi-pollutant degradation, catering for scalable water treatment applications.