Enhanced antibiotic degradation and sacrificial H₂ evolution via a heterointerface- and defect-engineered 2D/2D ZnIn₂S₄/BiOIO₃ S-scheme photocatalyst

Designing efficient and robust photocatalysts for both water treatment and sustainable energy production remains a significant challenge. Herein, we report a 2D/2D heterostructure composed of ZnIn₂S₄ (ZIS) and defect-engineered BiOIO₃ (DBOI), synthesized via an in situ hydrothermal method. The optimized ZIS/DBOI-30 photocatalyst exhibits enhanced bifunctional activity under simulated AM 1.5G illumination, achieving 99.8% degradation of moxifloxacin (MFX) within 60 min and high-rate sacrificial H₂ evolution (AQE 9.1% @ 360 nm) in independent tests. These results represent notable improvements over the individual ZIS, BOI, and DBOI components. Photodegradation assessments under varying water chemistry conditions, including pH, common ions, and catalyst dosage, demonstrate the photocatalyst's robustness and adaptability. Moreover, the catalyst maintained stable performance over eight successive cycles, with activity retention exceeding 90% for both MFX degradation (60 min per cycle) and sacrificial H₂ evolution (5 h per cycle). This enhanced dual-functionality is attributed to the abundant oxygen vacancies in DBOI and the intimate sheet-on-sheet interface with ZIS, which synergistically suppresses electron–hole recombination and enhances interfacial charge carrier migration. Furthermore, radical scavenging tests and ESR confirm the participation and formation of both ^•O₂⁻ and ^•OH species, while in situ light-irradiated XPS reveals opposite binding-energy shifts under illumination, together suggesting an S-scheme charge-transfer pathway that preserves strong redox potentials. This work highlights the critical importance of heterointerface engineering and defect modulation in achieving high-performance dual photocatalysis for water treatment and sacrificial hydrogen production, offering promising prospects for both environmental and energy applications.