N‐Doped Carbon Confined NiCo Alloy Hollow Spheres as an Efficient and Durable Oxygen Electrocatalyst for Zinc‐Air Batteries

Exploring cost‐efficient/durability bifunctional electrocatalysts are of upmost importance for the practical application of metal–air batteries. However, preparing bifunctional electrocatalysts with the above three advantages remains conceptually challenging. This work reports the preparation of N‐doped carbon confined NiCo alloy hollow spheres (NiCo@N−C HS) as bifunctional oxygen electrocatalyst for Zn‐air battery with a higher energy density (788.7 mWh gZn−1) and outstanding cycling stability (over 200 h), which are more durable than the commercialized Pt/C+RuO2‐based device. Electrochemical results and theoretical calculation demonstrate that the synergy in the NiCo@N−C accelerates the electronic transmission for improving activation of O2* and OH* intermediates and optimizing reacted free energy pathways, while the hollow structures exposure more active sites for improving the reaction kinetics and enhancing the activity of ORR/OER reaction. This work provides crucial understanding for constructing low‐cost transition metal‐based catalyst to overcome the efficiency and durability barriers of metal‐air batteries for widespread applications. NiCo@NC HS electrocatalyst with hollow structure have been constructed as a cost‐efficient/durability bifunctional oxygen electrocatalysts for Zn‐air batteries. The synergistic effect in NiCo@NC HS can promote the activation of O2* and OH* intermediates by modulating the electronic structure, and resulting enhanced OER/ORR activities.