Construction of Fe₃O₄@FeS₂@C@MoS₂ Z-scheme heterojunction with sandwich-like structure: Enhanced catalytic performance in photo-Fenton reaction and mechanism insight

Herein, the sandwich-like Fe₃O₄@FeS₂@C@MoS₂ composite was prepared via coating MoS₂ shell on the surface of core/shell Fe₃O₄@C composite. During the coating process, Fe₃O₄ was partly sulfurized to FeS₂, whose energy band was well-matched with that of MoS₂ for a Z-scheme heterojunction. The residual Fe₃O₄ ensured the rapid separation of heterojunction by magnet. In photo-Fenton reaction, 81.5% of tetracycline was degraded within 40 min, which was higher than the sum of degradation efficiency of Fenton reaction and photocatalytic reaction. 93.6% of the degradation efficiency in the 1st cycle was still maintained after 5 cycles. In mechanism study, the sources of ^•OH, ^•O₂^-, ¹O₂ and h⁺ were carefully traced, and the contributions of these radicals followed the order: ^•OH_surf>^•O₂^->¹O₂>h⁺>^•OH_free. An inner electric field was built at the interface by analyzing the energy band and work functions, which driven the charge carriers transfer followed a Z-scheme path. The findings in this manuscript were beneficial for designing catalysts with high photo-Fenton activity.