Modulating the Electronic Coordination Configuration and d-Band Center in Homo-Diatomic Fe2N6 Catalysts for Enhanced Peroxymonosulfate Activation

The electronic coordination configuration of metal active sites and the reaction mechanism were investigated by constructing homo-diatomic Fe sites for visible-light-assisted heterogeneous peroxymonosulfate (PMS) activation. A novel Fe₂N₆ catalyst was synthesized by selecting uniform pyridinic-N of graphitic carbon nitride (g-C₃N₄) as anchoring sites. The results demonstrated that homo-diatomic Fe sites modulated the d-band center and electron delocalization and thus enhanced the PMS activation kinetics (3.58 times vs single-atom Fe catalyst) with k_obs of 0.111 min^-1 owing to the synergistic effect between adjacent Fe atoms. New Fe-Fe coordination significantly decreased the contribution of the antibonding state in the Fe-O bond due to the coupling of the Fe-3d orbitals, which facilitated the O-O bond cleavage of the Fe₂-HOO-SO₃ complex with a reduced thermodynamic energy barrier of only -0.29 eV. This work provided comprehensive mechanistic insights into developing homo-diatomic catalysts governed by the coordination configuration and radical pathway for efficient heterogeneous PMS catalysis.