FeNC catalysts decorated with NiFe₂O₄ to enhance bifunctional activity for Zn–Air batteries

Rechargeable Zn–air battery is a promising next-generation energy storage device attributed to its high energy density, excellent safety, and low cost. However, its commercialization is hampered by sluggish kinetics of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) at air electrodes. Herein, we have designed, fabricated, and demonstrated a highly efficient ORR/OER electrocatalyst, NiFe₂O₄/FeNC, using low-cost materials via a facile synthesis route. NiFe₂O₄ is successfully loaded on Fe/N-doped carbon (FeNC) through bonding to Fe₃C in FeNC. Due to the existence of high ORR active sites such as FeN₄ and Fe and N-doped carbon moieties, the half-wave potential of the ORR reaches a high value of 0.83 V. While benefited from NiFe₂O₄ with high OER activity and the synergistic effect between NiFe₂O₄ and FeNC, the overpotential is 310 mV at 10 mA cm^–2 in the OER. The voltage difference between charging–discharging operations in the Zn–air battery employing the NiFe₂O₄/FeNC electrocatalyst only increases by 0.16 V after cycling for 100 h (600 cycles) at 10 mA cm^–2, which is much lower than 1.28 V using the best commercial Pt/C and RuO₂ catalysts.