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A novel type of covalent organic frameworks has been developed by assembling definite cobalt-nitrogen-carbon configurations onto carbon nanotubes using linkers that have varying electronic effects. This innovative approach has resulted in an efficient electrocatalyst for oxygen reduction, which is understood by a combination of in situ spectroelectrochemistry and the bond order theorem. The strong interaction between the electron-donating carbon nanotubes and the electronaccepting linker mitigates the trend of charge loss at cobalt sites, while inducing the generation of high spin state. This enhances the adsorption strength and electron transfer between the cobalt center and reactants/ intermediates, leading to an improved oxygen reduction capability. This work not only presents an effective strategy for developing efficient non-noble metal electrocatalysts through reticular chemistry, but also provides valuable insights into regulating the electronic configuration and charge behavior of active sites in designing high-performance electrocatalysts.

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Effective adjustment of the internal electron spin state and the external charge density of the metal is considered important for improving the catalytic activity of metal-nitrogen complex carbon (M/NC) electrocatalysts. Herein, we synthesize a FeMn/NC dual-atom catalyst with a local structure of FeN4–MnN4, which exhibits excellent oxygen reduction reaction (ORR) activity in acidic, neutral, and alkaline environments. In addition, the Zn–air battery based on the FeMn/NC catalyst has a high open-circuit voltage (1.27 V vs RHE), a satisfactory output power density (129 mW cm–2), and a strong charge and discharge stability (500 cycles), all of which are superior to those of commercial Pt/C. Such splendid catalytic performance is due to the change in the charge environment and the transition of the 3d orbital spin state at the metal center. Moreover, density functional theory calculations further demonstrate that the bimetallic synergy mechanism can optimize the adsorption energy of intermediates and improve the ORR efficiency. This work provides a new insight into the rational design of bimetallic catalysts with extraordinary comprehensive ORR capability.