Enhanced Oxygen Reduction Reaction Performance of Fe‐N 4 Single‐Atom Catalysts Through Fe 3 C Coupling

Abstract

Understanding the electronic factors contributing to the high oxygen reduction reaction (ORR) activity of Fe‐N 4 sites remains a significant challenge due to the localized Fe 3d orbitals and their sensitivity to the coordination environment. In this study, we report an Fe‐based porous carbon catalyst (Fe 3 C@Fe/NC), in which Fe‐N 4 moieties coexist with Fe 3 C nanoparticles within a porous carbon matrix. Electrochemical characterization exhibited an enhanced half‐wave potential of 0.912 V versus reversible hydrogen electrode (RHE) and excellent long‐term stability for Fe 3 C@Fe/NC, evidencing its superior ORR performance. Theoretical analysis revealed that the presence of Fe 3 C in proximity to Fe‐N 4 sites induces electronic interaction with the Fe centers, accompanied by changes in the distribution of axial 3d orbitals. Such electronic modulation could influence the interaction between Fe sites and oxygen‐containing intermediates. Density functional theory calculations indicated a significantly reduced energy barrier (0.50 eV) for the OH desorption step in Fe 3 C@Fe/NC compared to isolated Fe‐N 4 sites. Overall, the incorporation of Fe 3 C significantly modulates the electronic structure of Fe‐N 4 sites, thereby boosting ORR performance. These findings offer a robust strategy for designing high‐performance nonprecious metal electrocatalysts via carbide‐assisted engineering.