Enhanced Fe^IV═O Generation via Peroxymonosulfate Activation by an Edge-Site Engineered Single-Atom Iron Catalyst

As an oxidant, the ferryl-oxo complex (Fe^IV═O) offers excellent reactivity and selectivity for degrading recalcitrant organic contaminants. However, enhancing Fe^IV═O generation on heterogeneous surfaces remains challenging because the underlying formation mechanism is poorly understood. This study introduces edge defects onto a single-atom Fe catalyst (FeNC-edge) to promote Fe^IV═O generation via peroxymonosulfate (PMS) activation. In the presence of PMS, the FeNC-edge catalyst at a low dose (20 mg L^-1, equivalent to 0.14 mg L^-1 Fe) exhibits unprecedented activity for organic contaminant degradation. Electrochemical analysis, in situ Raman spectroscopy, and Fe^IV═O probe experiments confirm that Fe^IV═O generation is enhanced on the surface of FeNC-edge. Density functional theory calculations reveal that the introduced edge sites concentrate electron density on active Fe atoms, facilitating charge transfer from Fe to PMS. Notably, FeNC-edge immobilized on a polymeric membrane functioned as a continuous-flow oxidation system with efficient catalyst recycling and minimal Fe leaching.