Rational Design of a Co/MnO-Embedded 2D Nitrogen-Doped Carbon/Carbon Nanotube Hybrid Catalyst for Efficient Oxygen Catalysis and High-Capacity Zn–Air Batteries

Bimetallic catalysts used as air cathodes for Zn–air batteries offer improved activity and performance by tuning the electronic structure and interactions between metals. In particular, the fabrication of metal/metal compound heterostructure-embedded carbon catalysts is required owing to their desired properties; however, this often requires multistep-involved/complex synthesis conditions, hampering large-scale production. In this study, a Co/MnO-embedded nitrogen-doped carbon/carbon nanotube (CM-N:C) was developed by using a simple synthetic strategy that involved heat-treating the intermediate platform of a Co-based two-dimensional zeolitic imidazolate framework (2D ZIF). The 2D leaf-like products from the ZIF led to the exposure of abundant active sites, and the unique carbon/carbon nanotube hybrid structure resulted in the good durability of the developed catalysts. Moreover, owing to the heterojunction interface, modulated electronic configuration, and favorable porous features, the designed catalyst (CM-N:C) exhibited superior oxygen evolution and oxygen reduction catalytic activities. Furthermore, Zn–air batteries loading these catalysts demonstrated excellent performance, with an especially high specific capacity of 841.26 mAh/gzn and energy efficiency of 58.8% at 5 mA/cm2. This study provides a perspective for the development of efficient electrocatalysts and air cathode materials for sustainable energy conservation systems.