FeNi/NiFe2O4 hybrids confined in N-doped carbon sponge derived from Hofmann-type MOFs for oxygen electrocatalysis

Rational design of metal/metal oxide hybrids embedded in heteroatom-doped carbon is a desired strategy to improve the kinetics of oxygen reduction (ORR)/evolution (OER) reactions. Herein, we present an elaborate method for preparing FeNi-based bimetallic alloy/oxide hybrids implanted in spongy-like N-doped carbon (S-FeNi/NiFe2O4@NC) via introducing FeNi Hofmann-type metal-organic frameworks (MOFs) as pyrolysis precursors. Impressively, the evenly distributed FeNi alloys coexisting with oxides are directly derived from bimetallic nodes in the MOFs, which are expected to boost the intrinsic electrocatalytic activity by multi-compositional synergism. Meanwhile, spongy-like N-doped carbon matrix would be effective for achieving rich metal active sites and rapid mass/electron transport. Accordingly, the obtained S-FeNi/NiFe2O4@NC-800 shows an extraordinary electrochemical activity with an ORR/OER potential gap of 0.76 V. In addition, the catalyst emerges outstanding stability with potential losses that are only half those of commercial reference catalysts for both ORR and OER after 10,000 cycles. Importantly, zinc-air battery assembled with S-FeNi/NiFe2O4@NC-800 delivers a high peak power density of 129 mW cm−2 and an excellent specific capacity of 837 mA h g−1.