Electronic Structure Modulation of Fe‐N ₄ Sites by Heteroatom Doping in Hollow N‐Doped Carbon Spheres for Enhanced Oxygen Reduction Reaction

Covalent organic polymers (COP) have emerged as promising oxygen reduction reaction (ORR) catalysts due to their well‐defined and tunable structures. However, the influence of carbon substrates doped with heteroatoms of varying electronegativities on the electronic structure of active sites remains poorly understood. In this study, core‐shell structured COP FePc @XNC catalysts (X = F, Cl, or Br) were constructed by supporting FePc‐based covalent organic polymers (COP FePc ) on hollow N‐doped carbon spheres that were doped with heteroatom X. Experimental results reveal that the electron‐withdrawing capability of highly electronegative heteroatoms reduces the electron density at the Fe sites in COP FePc , thereby weakening the adsorption of oxygenated intermediates and accelerating the ORR kinetics. COP FePc @FNC exhibits outstanding ORR performance under alkaline conditions, with an onset potential (E 0 ) of 1.03 V and a half‐wave potential (E 1/2 ) of 0.912 V, surpassing the commercial Pt/C catalyst (E 0 = 1.01 V, E 1/2 = 0.85 V). The insights gained into heteroatom doping strategies in this study guide the rational design of carbon‐based electrocatalysts for enhanced performance.