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/g_zn 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.