Enhanced cycling of Fe(III)/Fe(II) and mass transfer strategy for efficient and stable activation of peroxydisulfate for water decontamination via a flow-through Fe-MOFs cathode

The efficiency and stability of the electrical activation of persulfate (PS) by transition metal-based cathode are controlled by the cycling of Fe(III)/Fe(II) and the mass transfer of PS. In this study, the mixed-valence MOFs catalyst (Fe^II-MIL-53(Fe)) modified flow-through cathode was prepared for the first time. Fe^II-MIL-53(Fe) was prepared by replacing part of the iron-oxygen network structure in MIL-53(Fe) with Fe(II), resulting in the formation of coordinated unsaturated iron centers (CUICs). The increase of the Fe(III) CUICs facilitated the conversion of Fe(III) to Fe(II). Furthermore, the cycling of Fe(III)/Fe(II) was further promoted by the electric field. Meanwhile, the hydrodynamic behavior of flow-through cathode was indicated by the computational fluid dynamics (CFD) simulation. The quenching experiments and electron paramagnetic resonance (EPR) results showed that several reactive specie (SO₄^·-, ·OH, O₂^·- and ¹O₂) were produce. In summary, this work provided an effective strategy for the efficient and stable electrical activation of PDS.