Biomimetic Square Pyramidal N1‐Fe‐N4 Single Sites with Optimized Electron Distribution for the Efficient Oxygen Reduction Reaction

Abstract Single atom iron‐nitrogen‐carbon (Fe‐N‐C) catalysts with a planar Fe─N 4 structure are widely investigated as potential alternatives to platinum‐based materials for oxygen reduction reaction (ORR), while they still suffer from the imperfect adsorption and activation of reaction intermediates, limiting their reduction efficiency. Herein, a Fe single‐atom catalyst with a biomimetic square pyramidal N 1 ‐Fe‐N 4 site supported by honeycomb‐like porous carbon (SA‐FeN 5 /HPC) is successfully prepared by a supramolecular confinement‐pyrolysis strategy. Theoretical calculations unveil that the introduction of spatially axial N ligands effectively regulates the charge redistribution around the planar Fe─N 4 active centers and confers Fe active moieties with appropriate adsorption strength for intermediates, thereby resulting in accelerated ORR kinetics. Consequently, the oversaturated SA‐FeN 5 /HPC catalyst showed excellent electrocatalytic ORR activity, achieving a half‐wave potential of 0.93 V versus RHE and superior durability. Moreover, Zn‐air batteries with SA‐FeN 5 /HPC as the cathode electrocatalyst displayed excellent performance, demonstrating great potential for practical application. This work paves the way for the design and development of high‐coordination single‐atom electrocatalysts.