Defect-interface co-regulated sulfur-vacancy-rich MoS2@Fe3O4/Ti3C2Tx MXene S-scheme heterojunction for dual-field-driven peroxydisulfate photoactivation.

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/Ti3C2Tx MXene (HSv-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 HSv-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 HSv-MoS2/Fe3O4 and HSv-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 HSv-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.