Core–Shell ZIF-8@ZIF-67-Derived Cobalt Nanoparticle-Embedded Nanocage Electrocatalyst with Excellent Oxygen Reduction Performance for Zn–Air Batteries

Metal–nitrogen–carbon (M–N–C) catalysts obtained from zeolitic imidazolate frameworks (ZIFs) have great potential in the oxygen reduction reaction (ORR). Herein, based on the same three-dimensional (3D) topological structure of ZIF-67 and ZIF-8, ZIF-67 is grown on the ZIF-8 surface by the epitaxial growth method, and ZIF-8 is used as a sacrificial template to obtain a Co-embedded layered porous carbon nanocage (CoPCN) electrocatalyst. Meanwhile, the self-sacrificing template effectively improves the specific surface area of the porous structure and reduces the depletion of active sites. The CoPCN shows a high half-wave potential of 0.885 V and superior stability as well as excellent methanol resistance. Theoretical calculations demonstrate that the Co–N1–C2 sites of CoPCN effectively reduce the energy barrier of ORR. In addition, a zinc–air battery (ZAB) based on the CoPCN exhibits excellent peak power density (90 mW cm–2) and superior cycle performance. This work presents a novel idea in the design of ZIF precursor systems to synthesize efficient ORR catalysts.