Graphene-wrapped bimetallic nanoparticles bifunctional electrocatalyst for rechargeable Zn-air battery

Developing efficient and stable bifunctional electrocatalysts towards oxygen evolution/reduction reactions (OER/ORR) is both critical and challenging for the application of zinc-air batteries (ZABs). In this work, a reduced graphene oxide-encapsulated, metal-organic framework (MOF)-derived NiCo bimetallic nanoparti-cles-based bifunctional catalyst (NiCo@rGO) was successfully prepared. The intertwining of flaky rGO and MOF derivatives results in a large specific surface area and abundant pore structure, which is favorable for exposure of active catalytic sites and ensures high electronic conductivity of the catalyst at the same time. The cooperation of cobalt and nickel nanoparticles enriches the active centers and increases the intrinsic cat-alytic activity compared with monometallic Co nanoparticles, leading to enhanced catalytic performance. Benefited from the above advantages, NiCo@rGO exhibits efficient catalytic activities with an oxygen reduc-tion half-wave potential of 0.85 V and oxygen evolution overpotential of 460 mV at 10 mA cm-2. Furthermore, the ZABs with NiCo@rGO exhibits a open-circuit voltage of 1.49 V, a peak power density of as high as 110.45 mW cm-2 and excellent stability over 180 h. This contribution paves a practical avenue to construct bimetal-rGO composites for high-performance ZABs.

Automated summary

In this study, a NiCo@rGO bifunctional catalyst was successfully prepared, which exhibited high catalytic activity and electronic conductivity due to its large specific surface area and abundant pore structure. It showed excellent performance in oxygen evolution/reduction reactions and zinc-air batteries.