A bimetallic 2D NiFe MOF/N-doped reduced graphene oxide as a bifunctional oxygen catalyst for rechargeable zinc-air batteries

The development of cost-effective, highly efficient, and stable bifunctional catalysts to replace precious metal-based electrocatalysts is essential for practical applications of rechargeable zinc-air batteries. In this work, two-dimensional bimetallic NiFe metal organic framework/nitrogen-doped reduced graphene oxide (2D NiFe MOF/N-rGO) was developed through a simple two-stage hydrothermal method. The uniformly distributed and closely packed 2D NiFe MOF nanosheets not only increase the specific surface area of the material but also provide abundant active sites for electrocatalytic reactions. The 2D NiFe MOF/N-rGO hybrid material exhibits a high bifunctional oxygen electrocatalytic activities (ΔE = 0.68 V) with a half-wave potential (E_1/2) of 0.8 V (vs. RHE) for oxygen reduction reaction (ORR) and an overpotential of 250 mV at 10 mA cm⁻² (η₁₀) for oxygen evolution reaction (OER), superior to the state-of-the-art Pt/C and RuO₂ catalysts. Moreover, a rechargeable zinc-air battery with NiFe MOF/N-rGO as a cathode catalyst delivers a peak power density of 146.8 mW cm⁻² and enhanced cycling stability, demonstrating its potential as a bifunctional catalyst with non-noble metal for metal-air batteries.