Ordered macroporous design of sacrificial Co/VN nano-heterojunction as bifunctional oxygen electrocatalyst for rechargeable zinc-air batteries

The development of efficient oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) bifunctional electrocatalysts is essential for rechargeable zinc-air batteries (ZABs). Herein, an ORR/OER bifunctional pre-catalyst consists of Co/VN heterojunction supported by N-doped carbon (NC) with three-dimensionally ordered macroporous (3DOM) architecture was fabricated. The VN was introduced as sacrificial promoter to facilitate the oxidization and self-reconstruction of Co into Co3O4 and CoOOH during OER process, which acts as the real active OER component. On the other hand, the Co-decorated N-doped carbon is the active species for ORR reaction. Meanwhile, the 3DOM structure design also provides a large specific surface area and exposes rich active sites. Benefiting from those advantages, the Co/[email protected] exhibits good activity and stability towards ORR and OER reactions comparable with commercial catalysts. Moreover, density functional theory calculations confirmed that Co3O4 and CoOOH exhibit higher adsorption energy for OH– and present an exothermic reaction in the OER process, which is beneficial to OER reaction. The ZABs using Co/[email protected] as bifunctional catalyst exhibits a high specific capacity of 775.68 mAh g−1 under 10 mA cm−2 and ultralong charge–discharge cycle life about 200 h at 20 mA cm−2. This work provides a new strategy of using sacrificial heterojunction for the development of efficient and durable bifunctional oxygen electrocatalyst.