Breaking the N-limitation with N-enriched porous submicron carbon spheres anchored Fe single-atom catalyst for superior oxygen reduction reaction and Zn-air batteries

Nitrogen-doped carbon supported metal single-atom catalysts (M-N-C SACs), especially Fe-N-C SACs appear as very promising catalysts for oxygen reduction reaction (ORR). However, precisely modulating of the Fe-Nx configuration and geometric microenvironment in Fe-N-C SACs to achieve the highest level of catalytic activity remains grand challenges. Herein, we describe a N-rich heterocycle regulated supramolecular coordination self-assembly strategy to fabricate Fe single atoms anchored on N-enriched porous submicron carbon spheres (FeSA/N-PSCS), with ultra-high N-dopant content (14.81 at.%) for facilitating the formation of atomically dispersed Fe-N4. Density functional theory calculations validate that N-doping at the periphery of the Fe-N4 active sites optimizes the adsorption of oxygen-containing intermediates and significantly reduces the ORR overpotential. Benefitting from the localized N-enriched atomic configuration, highly microporous, and regular submicron-spherical structure, FeSA/N-PSCS exhibit enhanced ORR performance. More importantly, FeSA/N-PSCS catalyzed Zn-air battery (ZAB) outperforms Pt/C+RuO2-based ZAB in the aspects of maximum power density, specific capacity and cycling stability.