Rapid preparation of a Fe coordination structure adjustable ORR catalyst using microwaves with a half-wave potential above 0.9 V

Abstract

An oxygen reduction reaction (ORR) catalyst is a crucial component of metal–air batteries. Herein, modified carbon nanotubes are used to support iron phthalocyanine, followed by the fabrication of single-atom and cluster coexisting catalysts by the fast microwave method. The two catalysts have Fe–N₅ and Fe–P–N₄ coordination structures, respectively. Electrochemical tests show that the Fe_NC/Fe–N₅–C and Fe_NC/Fe–P–N₄–C catalysts have half-wave potentials of 0.906 and 0.886 V in an alkaline solvent, respectively. The Zn–air battery prepared with the Fe_NC/Fe–N₅–C catalyst has a specific capacity of 791 mA h g⁻¹ and a maximum power density of 190 mW cm⁻². DFT calculations show that the axial coordination bonds in Fe_NC/Fe–N₅–C and Fe_NC/Fe–P–N₄–C are conducive to the acceleration of the transfer of electrons. The d-band centers of the axial coordination Fe–N₅ and Fe–P–N₄ are closer to the Fermi level, confirming that the presence of the axial coordination bonds enhances the adsorption of the reaction intermediates and reduces the ORR barriers.