Refining Asymmetric Low-Coordinated Fe-N₃ Motif to Boost Catalytic Ozonation Activity

In the quest to boost the intrinsic activity of single-atom catalysts (SACs), optimizing the electronic properties of metal centers and maximizing active sites play a pivotal role. Here, a facile surface molten salt-assisted approach for fabricating porous iron-nitrogen-carbon catalysts enriched with catalytically accessible single-atom motifs is reported. Multiple characterization analyses prove that abundant intrinsic defects are generated at the edge sites, resulting in the formation of thermally stable unstitched Fe-N-3 motif. Theoretical investigations unveil that the transition from Fe-N-4 to Fe-N-3 induces structural alteration, resulting in the convergence of Fe-3d orbital energy to Fermi energy. The low-coordinated Fe-N-3 motif exhibits higher activation ability, reinforcing its interaction with O-3 and weakening the O-O bond. This leads to a reduction in the reactivity of surface atomic oxygen barriers (O-3-to-*O/*OO), ultimately achieving efficient catalytic oxidation of methyl mercaptan and its intermediates, achieving performance 20-fold higher than intact Fe-N-4 catalysts and 625-fold higher than commercial MnO2. These findings present a comprehensive approach for synthesizing SACs with fully accessible active sites and boosted electronic configurations to advance catalytic ozonation activity.