FeNC Catalysts Decorated with NiFe₂O₄ to Enhance Bifunctional Activity for Zn-Air Batteries

Rechargeable Zn-air battery is a promising next-generationenergy storage device attributed to its high energy density, excellentsafety, and low cost. However, its commercialization is hampered bysluggish kinetics of the oxygen reduction reaction (ORR) and oxygenevolution 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 afacile synthesis route. NiFe2O4 is successfullyloaded on Fe/N-doped carbon (FeNC) through bonding to Fe3C in FeNC. Due to the existence of high ORR active sites such asFeN(4) and Fe and N-doped carbon moieties, the half-wavepotential of the ORR reaches a high value of 0.83 V. While benefitedfrom NiFe2O4 with high OER activity and thesynergistic effect between NiFe2O4 and FeNC,the overpotential is 310 mV at 10 mA cm(-2) in theOER. The voltage difference between charging-discharging operationsin the Zn-air battery employing the NiFe2O4/FeNC electrocatalyst only increases by 0.16 V after cycling for100 h (600 cycles) at 10 mA cm(-2), which is muchlower than 1.28 V using the best commercial Pt/C and RuO2 catalysts.