Molecular Template Engineering Hierarchical Porous Fe-N-C with Tunable Fe3O4 Particle Size for Efficient Oxygen Reduction Reaction

Synergistic effect between M-NX sites and MXOY particles in hierarchical porous M–N-C catalysts holds great promises in boosting oxygen reduction reaction (ORR). In this work, 1,4-dicyanobenzene was utilized as a molecular template to prepare the hierarchical porous Fe–N-C catalysts with size-tunable Fe3O4 particles for enhanced ORR in Zn-air battery. The as-prepared Fe3O4#Fe–N/CDB0.1 owned a half-potential of 0.90 V vs RHE, exceeding that of commercial 20%Pt/C (E1/2 = 0.82 V vs RHE), showing a maximum power density of 321 mW cm−2 in a homemade Zn-air battery. Density functional theory (DFT) calculations indicate that the electronic interaction between Fe3O4 and Fe-N4 sites enhances the adsorption energy of *OOH, effectively optimizing the energy barrier for *O formation, significantly reducing the limiting energy barrier. Such superior ORR activity in Fe3O4#Fe–N/C originated from the optimized hierarchical pores and synergistic effect between Fe-NX sites and Fe3O4 particles. This work provides a new and facile template strategy for engineering hierarchical porous carbon-based materials to achieve highly efficient catalytic reactions.