Designing superior bifunctional electrocatalyst with high-purity pyrrole-type CoN4 and adjacent metallic cobalt sites for rechargeable Zn-air batteries

Developing cost-effective and high-efficient bifunctional electrocatalyst for both oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is essential for rechargeable Zn-air battery application. However, achieving high-active dual sites for bifunctional oxygen electrocatalysis in a single catalyst, as well as determining the decisive active sites for OER and ORR to explore the synergistically catalytic mechanism remain challenges. Herein, we propose a catalyst consisting of high-purity pyrrole nitrogen anchored cobalt single-atom (CoN 4 ) and adjacent metallic cobalt sites (Co p @CoNC) for explicit research of dominated active sites. The obtained Co p @CoNC exhibits superior electrocatalytic activity with a small overpotential difference of 0.68 V between OER potential at 10 mA cm −2 and ORR half-wave potential, outperforming commercial noble-metal based catalysts. Electrochemical measurements and theoretical simulations verify the pyrrole-type CoN 4 and adjacent metallic cobalt are separately decisive active sites for ORR and OER activities. Simultaneously, metallic cobalt regulates electron distribution of CoN 4 moiety to improve ORR activity. Importantly, the rechargeable liquid and flexible solid-state Zn-air batteries using Co p @CoNC as air electrode catalysts possess high peak power densities of 188.8 and 121.8 mW cm −2 , respectively. Our findings provide a feasible strategy to design high-performance multifunctional catalysts for rechargeable Zn-air batteries application.