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 kobs 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.