Rational Design of an FeCo₂O₄@FeCo₂S₄ Heterostructure as an Efficient Bifunctional Electrocatalyst for Zn–Air Batteries

The development of active, robust, and nonprecious electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is essential to improve the performance of Zn–air batteries (ZABs). Here, we present the FeCo2O4@FeCo2S4 heterostructure in situ decorated on Ni foam as bifunctional electrocatalysts to trigger ORR and OER. Owing to the large electrochemical active surface area and synergistic effects at interfaces, the FeCo2O4@FeCo2S4/NF exhibits an OER overpotential of 283 mV at 10 mA cm–2, excellent robustness with negligible variation during continuous linear sweep voltammetry cycles, and an onset potential (Eonset) of 0.89 V (vs RHE) for ORR. Furthermore, the FeCo2O4@FeCo2S4/NF-triggered ZAB achieves a high power density of 189.75 mW cm–2 at 10 mA cm–2. In particular, the rechargeable ZAB with FeCo2O4@FeCo2S4/NF displays a small charge–discharge voltage gap and good cycle performance of up to 227 h at 10 mA cm–2.