Well-dispersed Ni3Fe nanoparticles with a N-doped porous carbon shell for highly efficient rechargeable Zn-air batteries.

NiFe-based nanoparticles attached to heteroatom-doped carbon are found to act as tremendously efficient oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) electrocatalysts. Nevertheless, it is extremely challenging to control the particle size and avoid aggregation. Herein, nitrogen-doped carbon encapsulated Ni3Fe nanoparticles (Ni3Fe@NC) are prepared by two-stage pyrolysis with a low rate based on the in situ structural evolution of FeNi-PBAs. The strategy results in uniform Ni3Fe nanoparticles anchoring within the carbon shell and thus facilitating interfacial interaction. Benefiting from the enhanced synergism between Ni3Fe particles and NC layers, Ni3Fe@NC-600 demonstrates the best catalytic activity and durability, not only with almost the same onset potential (1.01 V) as commercial Pt/C for the ORR but also satisfactory OER performance with a low overpotential of 0.29 V at 10 mA cm-2 in 0.1 M KOH. Moreover, the Zn-air battery assembled using the Ni3Fe@NC-600 cathode exhibits superior performance to commercial Pt/C + RuO2. The simple and scalable method of this work provides insight into the fabrication of high-performance and cost-effective bifunctional oxygen electrocatalysts.