A Versatile Extended Stöber Approach to Monodisperse Sub‐40 nm Carbon Nanospheres for Stabilizing Atomically Dispersed Fe─N4 Sites Toward Efficient Oxygen Reduction Electrocatalysis

Abstract The development of atomically dispersed iron‐nitrogen‐carbon (Fe─N─C) catalysts as an alternative to precious platinum holds great potential for the substantial progress of a variety of oxygen reduction reaction (ORR)‐associated energy conversion technologies. Nevertheless, the precise synthesis of Fe─N─C single atomic catalysts (SACs) with a high density of accessible active sites and pronounced electrocatalytic performance still remains an enormous challenge. Herein, an innovative extended Stöber method is designed for the controllable preparation of monodisperse small‐sized N‐doped carbon colloidal nanospheres (≈40 nm) anchoring atomically isolated Fe─N 4 sites (abbreviated as Fe‐SA@N‐CNSs hereafter) with a narrow size distribution and high uniformity. Benefiting from the single Fe─N 4 moieties and the unique spherical carbon substrate, the resultant Fe‐SA@N‐CNSs exhibit excellent ORR activity, outstanding long‐term durability, and methanol tolerance in KOH electrolyte. More impressively, when further assembled into a flexible solid‐state rechargeable zinc–air battery (ZAB), the Fe‐SA@N‐CNSs‐driven ZAB delivers a higher open circuit voltage, a larger power density, and robust cycling/mechanical stability, outperforming the state‐of‐the‐art Pt/C‐based counterpart and further testifying the great potential of the as‐prepared Fe‐SA@N‐CNSs in diverse ORR‐related practical energy devices. The developed extended Stöber method provides an efficient and versatile avenue toward the preparation of a series of well‐defined SACs for diverse electrocatalytic systems.