Single-atomic Mn sites coupled with Fe3C nanoparticles encapsulated in carbon matrixes derived from bimetallic Mn/Fe polyphthalocyanine conjugated polymer networks for accelerating electrocatalytic oxygen reduction

The construction of robust coupling catalysts for accelerating electrocatalytic oxygen reduction reaction (ORR) through the modulation of the electronic structure and local atomic configuration is critical but remains challenging. Herein, we report a facile and effective isolation-polymerization-pyrolysis (IPP) strategy for high-precision synthesis of single-atomic Mn sites coupled with Fe3C nanoparticles encapsulated in N-doped porous carbon matrixes (Mn SAs/Fe3C NPs@NPC) catalyst derived from predesigned bimetallic Fe/Mn polyphthalocyanine (FeMn-BPPc) conjugated polymer networks by solid-phase reaction approach. Benefiting from the synergistic effects between the single-atomic Mn-N4 sites and Fe3C NPs as well as the confinement effect of NPC, the Mn SAs/Fe3C NPs@NPC catalyst exhibited excellent electrocatalytic activity and stability for ORR. The assembled Zn-air battery displayed larger power density of 186 mW·cm−2 than that of Pt/C + Ir/C-based battery. It also exhibits excellent stability without obvious voltage change after 106 cycles with 36 h. Combing in-situ Raman spectra with in-situ attenuated total reflectance surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) characterization results indicated that the Mn-N4 site as an active site for the O2 adsorption-activation process, which effectively facilitates the generation of key *OOH intermediates and *OH desorption to promote the multielectron reaction kinetics. Theoretical calculation reveals that the excellent electrocatalytic performance originates from the charge redistribution and the d orbital shift resulting from Mn-Fe bond, which buffers the activity of ORR through the electron reservoir capable of electron donation or releasing. This work paves a novel IPP strategy for constructing high-performance coupling electrocatalyst towards the ORR for energy conversion devices.