Construction of Covalent Organic Polymers with Single Cobalt Sites via a Pyrolysis-Free Strategy as a Bifunctional Oxygen Catalyst for Zinc–Air Batteries

Covalent organic polymers (COPs) are widely used in electrochemical catalysis due to their designable framework structure, controllable porosity, and well-defined catalytic centers. However, subsequent pyrolysis is usually required due to its inherent poor electrical conductivity, resulting in undesirable structural changes and destruction of the original fine structure. Herein, we prepared two single-Co-sites electrocatalysts with different structures by compositing highly conductive multiwalled carbon nanotubes (CNTs) with COPs having good liquid-processable properties as well as clear Co–N4–C structures via a pyrolysis-free strategy. Characterization by multiple techniques shows that the obtained catalysts improve the electrical conductivity while maintaining the atomically precise controllability. As a result, Co-BDTA-COP@CNT exhibited a low oxygen electrode gap of 0.810 V (ΔE = EJ=10 – E1/2). The Co-BDTA-COP@CNT catalyst delivers an unprecedented peak power density of 164 mW cm–2 for a zinc–air battery (ZAB), along with significantly higher durability. Density functional theory (DFT) calculations show that the introduction of long-chain aldehyde groups can improve the electronic structure of the Co active site and thus enhance the oxygen electrocatalytic performance.