Boosting Oxygen Reduction Reaction via N, S-Doped Carbon Shell-Encapsulated Fe₅C₂: Leveraging Lateral and Axial Synergy

Herein, a novel oxygen reduction reaction (ORR) electrocatalyst, consisting of an N,S-codoped carbon shell encapsulating Fe5C2 nanoparticles, is developed through self-assembled supramolecular structures and controlled pyrolysis. The resulting Fe5C2@SNC catalyst exhibits exceptional electrocatalytic performance, with a high half-wave potential (E1/2) of 0.86 V, comparable to that of commercial Pt/C. The distinctive core–shell structure contributes to excellent stability, demonstrating an 89% current maintenance after 20 h of continuous chronoamperometry testing. In Zn-air battery applications, the catalyst achieved a peak power density of 222 mW cm–2, surpassing that of its Pt/C counterpart. Combining the experiments and density functional theory calculations, the synergistic effects of axial Fe5C2 nanoparticles and laterally SOx-functionalized Fe–Nx carbon planes within Fe5C2@SNC have been comprehensively unveiled. The electron-withdrawing nature of sulfur leads to charge redistribution, particularly on N sites proximal to the SOx group. Additionally, the axial Fe5C2 nanoparticles have precisely modulated the d-band center of the Fe5C2@SNC catalyst, optimizing oxygen intermediate adsorption and enhancing the ORR activity. This work highlights the understanding and harnessing of synergistic catalysis via a controllable core–shell structure, providing an effective way for developing highly efficient and stable electrocatalysts for energy conversion and storage applications.