Macrocycle-based covalent-organic-polymer as efficient oxygen electrocatalysts for zinc-air flow batteries

Covalent organic polymers (COPs), as emerging porous materials with well-defined architectures and high hydrothermal stability, have attracted extensive attention in the field of electrocatalysis. Herein, we report a rational design method for preparing oxygen reduction reaction electrocatalysts with the assistance of a predesigned macrocyclic COP model molecular. With the predesigned nitrogen position and structural features in macrocyclic chain-like COP-based materials, the obtained COPMCT-Co-900 catalyst provided excellent oxygen reduction performance, where the half-wave potential (E1/2) reaches 0.85 V (vs . RHE), comparable to commercial Pt/C. We also extended the strategy to similar macrocycle COPs and Fe-based and Ni-based metal sources and studied the oxygen reduction reaction performance of corresponding catalysts, proving the universality of the method. Interestingly, we assemble COPMCT-Co-900 catalyst as air electrode catalyst of the self-made rechargeable zinc-air flow batteries, which exhibit outstanding power density (155.6 mW·cm-2) and long cycle life (90 h, 270 cycles at 10 mA·cm-2). Our studies provide a new method for the development of high-performance oxygen electrodes applied in zinc-air flow battery devices.