Interfacial-Bond Built-In Electric Field in S-Vacancy SnS ₂ /rGO Membranes Enables Full-Spectrum Photothermal Catalytic U(VI) Removal

The efficient treatment of uranium-contaminated water bodies is a challenge for the sustainable development of nuclear energy. Therefore, we developed a novel composite membrane (V-SnS₂/rGO) comprising an interconnected sulfur-vacancy SnS₂ scaffold encapsulated within cross-linked reduced graphene oxide. This unique structural design imparts the V-SnS₂/rGO membrane with strong absorption across the entire solar spectrum. Moreover, the photothermal conversion capability of rGO, combined with its rapid heat transfer to the V-SnS₂ catalyst, synergistically accelerates catalytic reaction kinetics. The optimized V-SnS₂/rGO-2 membrane achieves a U(VI) removal efficiency exceeding 79.1% within 1 h under full-spectrum irradiation, a performance that surpasses that of most reported catalysts. The reaction rate constant reached 0.099 min^-1 without any sacrificial agents in air, representing a 2.25-fold increase compared to V-SnS₂. The presence of sulfur vacancies induced the formation of asymmetric S-O units at the V-SnS₂/rGO interface, generating a polarized built-in electric field that efficiently promotes charge separation and transfer. Consequently, the increased electron density on the surface of V-SnS₂/rGO-2 facilitates oxygen molecule activation and the formation of superoxide radicals, enhancing H₂O₂ generation and ultimately converting U(VI) into insoluble (UO₂)O₂·2H₂O. This work provides a strategic approach to designing photothermal catalytic membranes through defect engineering and interfacial bond modulation.