Zn, Co, and Fe Tridoped N–C Core–Shell Nanocages as the High-Efficiency Oxygen Reduction Reaction Electrocatalyst in Zinc–Air Batteries

Transition metal–nitrogen–carbon (TM–N–C) nanomaterials are promising platinum-based substitutes for the oxygen reduction reaction (ORR). However, large-scale commercial production of high-efficiency, durable TM–N–C catalysts remains a formidable challenge. In this work, a facile ″ZIF-on-ZIF″ strategy is first adopted to design ZIF-8@ZIF-67 core–shell polyhedral nanocages, and then, ferrocene (Fc) is added to form ZIF-8@ZIF-67@Fc double-layer encapsulating polyhedral nanocages. Finally, Zn, Co, and Fe tridoped N–C nanocages (ZnCoFe–N–C) as the high-efficiency ORR electrocatalyst are prepared through high-temperature annealing. Benefiting from the trimetal, nitrogen and carbon species bond to each other to form highly efficient active sites, and the material exhibits outstanding performance in 0.1 M KOH, onset potential and half-wave potential of up to 0.95 and 0.878 V (vs RHE), respectively, and long-term durability and methanol tolerance. Furthermore, when utilizing as a zinc–air battery (ZAB) air electrode, it exhibits wonderful indicators, reflected in an open circuit voltage of 1.525 V, power density of 350.2 mW cm–2, and specific capacity of 794.7 mAh gzn–1, which outperforms the benchmark Pt/C catalyst. This work provides a facile and effective strategy to obtain a highly efficient and stable TM–N–C electrocatalyst for the ORR in ZABs.