Synergy of Pyridinic-N and Co Single Atom Sites for Enhanced Oxygen Redox Reactions in High-Performance Zinc-Air Batteries

Cobalt single-atom catalysts (SACs) have the potential to act as bi-functional electrocatalysts for the oxygen-redox reactions in metal-air batteries. However, achieving both high performance and stability in these SACs has been challenging. Here, a novel and facile synthesis method is used to create cobalt-doped-nitrogen-carbon structures (Co-N-C) containing cobalt-SACs by carbonizing a modified ZIF-11. HAADF-STEM images and EXAFS spectra confirmed that the structure with the lowest cobalt concentration contains single cobalt atoms coordinated with four nitrogen atoms (Co-N₄). Electrochemical tests showed that this electrocatalyst performed exceptionally well in both oxygen reduction reaction (ORR) (E1/2 ≈ 0.859 V) and oxygen evolution reaction (OER) (Ej = 10: 1.544 V), with excellent stability. When used as a bi-functional electrocatalyst in the air cathode of a rechargeable zinc-air battery (ZAB), a peak power density of 178.6.1 mW cm⁻², a specific capacity of 799 mA h g_Zn⁻¹ and a cycle-life of 1580 is achieved. Density functional theory (DFT) calculations revealed that the concentration and the position of the pyridinic nitrogen with Co play a critical role in determining the overpotential of this electrocatalyst for oxygen-redox reactions. The unprecedented performance of this electrocatalyst can bring paradigm changes in the practical realization and application of metal-air batteries.