π-Conjugated Macrocycles Confined Dual Single-Atom Catalysts on Graphitized Bubbles for Oxygen Reduction, Evolution, and Batteries

It is a great demand to develop high-performance electrodes for metal–air batteries to boost cathodic oxygen reduction/evolution dynamics and avoid anodic dendrites. The optimization of catalysis at electrode can be conducted by increasing effective surface exposure, active site density, and unsaturated coordination, via using metal clusters or atomic catalysts, along with conductive or defective supports. Herein, the polarized and synergistic cooperation between dual single atom sites (Fe-N₄/Co-N₄) are developed through electrolytical exfoliation of defect-enriched π-conjugated macrocyclic polyphthalocyanines to expose more active sites on hollow carbonized shells (HCS). Such FeCo-N₄/HCS exhibits outstanding performance in oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), to achieve high-performance in an aqueous zinc battery (AZB) with a high discharge capacity (763.6 mAhg⁻¹) after 750 cycles at 10 mA cm⁻², showing stable discharge voltage and excellent durability. It also possesses high performance in a lithium-O₂ battery owing to abundant defects, synergistic Fe-N₄/Co-N₄ active sites, reduced energy barriers, and boosted charge and mass transfer and reaction kinetics. This study provides novel perspectives to expand dual single-metal catalysts on macrocycles in the exploration of efficient, durable, and eco-friendly energy devices.