Pyridinic-N Regulated Electron Injection to Modulate *OH Adsorption at Fe–N–C Sites for an Efficient Oxygen Reduction Reaction

Abstract

To enhance the efficiency of oxygen reduction reaction (ORR) catalysts, precise control over the adsorption/ desorption energy barriers of oxygen intermediates at atomically dispersed Fe−N−C sites is essential yet challenging. Addressing this, we employed a pyrolysis approach using a nitrogen-containing polymer to fabricate Fe single-atom (SA) catalysts embedded in a pyridinic-N enriched carbon matrix. This synthesis strategy yielded Fe SAs that demonstrated a superior electrochemical ORR performance, evidenced by an impressive half-wave potential of 0.941 V and a high limiting current density of 5.72 mA/cm 2 . Moreover, when applied in homemade Zn−air batteries, this premier catalyst exhibited exceptional specific capacity (720 mAh/ g Zn ), peak power density (253 mW/cm 2 ), and notable long-term stability. Theoretical insights revealed that the increased pyridinic-N content in the catalyst facilitated efficient electron transfer from N atoms to the Fe active sites, thus fine-tuning the d-band center and effectively controlling the adsorption energy barrier of *OH species. These mechanisms synergistically improve the ORR performance. Crucially, this fabrication method shows promise for adaptation to other transition metal-based SAs, including Co, Ni, and Cu, potentially establishing a versatile synthesis route for developing atomically dispersed catalyst systems in future applications.