Atomically Dispersed Fe‐N₄ Bridged with MoO_x Clusters as a Bifunctional Electrocatalyst for Rechargeable Zn‐Air Battery

Abstract Bifunctional oxygen electrocatalysts with low cost, high activity, and long‐term durability are highly desired for rechargeable zinc‐air batteries (RZABs). However, the design of such catalysts is a significant challenge. Herein, a new bifunctional electrocatalyst composed of atomically dispersed Fe‐N 4 sites bridged with MoO x clusters (FeN 4 /MoO x ) on carbon black substrate is designed for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) involved in liquid and flexible RZABs. The FeN 4 /MoO x is prepared by pyrolyzing hematin porcine adsorbed on carbon black, followed by hydrothermal growth of MoO x . In the FeN 4 /MoO x catalyst, the Fe atoms are atomically dispersed and penta‐coordinated with four pyrrolic N atoms and one O atom of MoO x clusters. Such a structure produces strong electronic interactions between the Fe and Mo atoms. The FeN 4 /MoO x electrocatalyst exhibits excellent ORR and OER activities, with an ORR half‐wave potential of 0.902 V, an OER overpotential of 337 mV at 10 mA cm −2 , and an ultrasmall potential gap of 0.665 V. Liquid and flexible RZABs based on the FeN 4 /MoO x catalyst show a high energy and power density, as well as excellent cycling stability and rechargeability. This work introduces a novel type of bifunctional catalysts consisting of connected single atoms and clusters for energy storage devices and wearable electronics.