Novel Fe7S8/C nanocomposites with accelerating iron cycle for enhanced heterogeneous electro-Fenton degradation of dyes

Fe 3+ /Fe 2+ interconversion is one of the key factors for heterogeneous electro-Fenton degradation of organic pollutants. In this study, MIL-101Fe-derived carbon wrapping Fe 7 S 8 nanocomposite (Fe 7 S 8 /C-1-600) exhibits outstanding rhodamine B (RhB) degradation ability with extremely low iron leaching and high recyclable degradability within 60 min in a wide pH range. Moreover, Fe 7 S 8 /C-1-600 presents a much higher activity for RhB degradation than Fe 3 O 4 counterpart without sulfidation, which could be mainly attributed to the accelerated Fe 3+ /Fe 2+ cycling by iron with both multiple valences (Fe 0 , Fe 2+ , and Fe 3+ ) and sulfur species (S 2− and S 2 2− ) of the catalyst. The enhancement of H 2 O 2 adsorption and activation into OH on Fe 7 S 8 surface is confirmed by density functional theory calculations with respect to that on Fe 3 O 4 . Interestingly, SO 4 · − can be generated by reacting S 2 2− with dissolved O 2 and subsequently converted into ·OH, which further facilitates RhB degradation. These findings may shed a new insight into the potential application of metal sulfides for wastewater treatment.