Regulating the Fe-Nx coordination structure of Fe single-atom catalysts for efficient catalytic degradation of methylparaben

The catalytic activity of atomically dispersed FeNx structure toward perxoymonosulfate (PMS) is closely related to its coordination environment. However, the role different FeNx coordination structure in the interface catalytic reaction between Fe active center and PMS remains to be unraveled. Herein, N-modulated FeNx sites with different coordination structure in PMS activation for methylparaben (MeP) degradation was systematically investigated. FeN3 structure with unsaturated coordinating N atoms exhibits the highest MeP catalytic degradation performance, achieving a degradation efficiency of 99.7 % and a kinetic rate constant of 0.182 min(-1). The activity of FeNx site clearly decreased as the number of coordinating N atoms increased to 4 similar to 5 (FeN4 and FeN5). Synchrotron radiation analysis and theoretical calculations demonstrate that the unsaturated coordinating (FeN3) structure increases the local electron density of Fe moiety, leading to a upshift of the Fe d-band center close to the Fermi energy level. The unsaturated FeN3-C moiety optimizes the interaction energy between Fe atom and the PMS molecule, accelerating the production of high-valent Fe species for rapid MeP elimination. This study provides fundamental and technological insights into the correlation between coordination structure and high-efficiency catalytic activity of Fe single-atom catalysts for PMS activation.