Coupling of indium clusters with atomic Fe–N4 on carbon for long-term rechargeable Zn–air batteries†

Single atom electrocatalysts with typical metal–nitrogen–carbon sites possess good oxygen reduction reaction (ORR) activity, yet challenges remain in fabricating rechargeable zinc–air batteries (ZABs) due to their poor oxygen evolution reaction (OER) performance. Herein, we demonstrated the in situ anchoring of indium clusters on a carbon matrix with iron–nitrogen–carbon sites via the pyrolysis of supermolecule aggregates coordinated with indium and iron ions, aimed to prepare advanced bifunctional electrocatalysts for the ORR and OER. A detailed atomic structure analysis reveals that the modulation of the coordination environment between the indium cluster and iron–nitrogen–carbon sites induces asymmetrical charge distribution to reduce the reaction barrier via the p–d orbital hybridization, thus achieving superior bifunctional electrocatalytic activity. Consequently, the rechargeable ZABs demonstrated a cycling durability of 1650 h. Moreover, the solid-state batteries also exhibited a large power density of 220.0 mW cm⁻². This work provides a feasible guidance for rational incorporation of metal clusters with single atom sites to enhance bifunctional electrocatalysis.