Defect-interface co-regulated sulfur-vacancy-rich MoS₂@Fe₃O₄/Ti₃C₂T_x MXene S-scheme heterojunction for...

Visible-light-driven peroxydisulfate (PDS) activation is hindered by the high stability of the peroxide (OO) bond in PDS, magnetic aggregation of Fe₃O₄, and sluggish interfacial charge transfer. Herein, a sulfur-vacancy-rich MoS₂@Fe₃O₄/Ti₃C₂T_x MXene (HS_v-MoS₂@Fe₃O₄/MXene) S-scheme heterojunction was constructed by integrating sulfur-vacancy engineering with interfacial electric-field regulation for PDS activation and bisphenol A (BPA) degradation. The HS_v-MoS₂ shell suppressed Fe₃O₄ aggregation, while its coordinatively unsaturated Mo sites enhanced PDS adsorption and promoted OO bond polarization. Meanwhile, MXene provided a rapid electron-transport pathway. Cascade charge redistribution across the HS_v-MoS₂/Fe₃O₄ and HS_v-MoS₂@Fe₃O₄/MXene interfaces generated dual built-in electric fields that drove directional migration of photogenerated charge carriers through an S-scheme pathway, thereby enhancing electron availability and facilitating OO bond cleavage in PDS. The optimized system achieved an apparent rate constant of 0.109 ± 0.008 min^-1, 3.3 and 2.3 times the corresponding values for Fe₃O₄ and HS_v-MoS₂@Fe₃O₄, respectively. The system also exhibited good applicability in real water matrices, while the catalyst retained a BPA removal efficiency above 85% after five successive cycles. Theoretical calculations and multiscale interfacial characterization demonstrated that sulfur vacancies, MXene-mediated electron transport, and dual-electric-field-driven charge separation synergistically promoted PDS activation, with both radical and nonradical pathways contributing to BPA removal. This study establishes a defect-interface cooperative regulation strategy for photocatalytic PDS activation and provides mechanistic insights for the rational design of highly efficient environmental catalysts.