Engineering Co/CoO heterojunctions stitched in mulberry-like open-carbon nanocages via a metal-organic frameworks in-situ sacrificial strategy for performance-enhanced zinc-air batteries

Hollow nanocages are receiving immense research interest in oxygen redox electrocatalysis owing to their well-defined interior space and large surface areas. However, the conventional enclosed hollow nanostructures suffer from their large mass transfer resistance and incompletely exposed internal space. Herein, we develop a facile metal–organic framework (MOF) in-situ self-sacrificial template strategy for fabricating Co/CoO heterojunction stitched in mulberry-like hollow N-doped carbon (Co/[email protected]) towards oxygen electrocatalysis. The shell of Co/[email protected] is composed of N-doped carbon nanosphere subunits with abundantly dispersive Co/CoO heterojunction and open mass transfer channel. Benefiting from the abundant mass transfer channel of the mulberry-like hollow architecture and unique electronic properties by Co/CoO heterojunction and N-doping, as-fabricated Co/[email protected] affords more exposed internal space and accessible active site, thus facilitating the catalyst enhanced bifunctional oxygen electrocatalytic activity with a potential discrepancy (ΔE) of 0.83 V, far excelling the noble-metal-based Pt/C (0.99 V) and RuO2 (1.05 V). The Co/[email protected] based zinc-air battery (ZAB) renders a higher energy density of 920.5 Wh kgZn-1 and superior discharge/charge stability (over 250 h) than those of commercial Pt/C+RuO2 hybrid based ZAB (856.2 Wh kgZn-1, less than 100 h). The present work may offer a new way for engineering hollow materials for various energy-related applications.