Fe₃O₄/Fe₃C@Nitrogen‐Doped Carbon for Enhancing Oxygen Reduction Reaction

Abstract Oxygen reduction reaction (ORR) catalysts play a key role in energy conversion and storage devices. The preparation of iron‐based carbon materials as non‐precious metal catalysts with a simple and scalable method still presents significant challenges. In this work, partially oxidized Fe embedded in Fe₃C nanoparticles encased in nitrogen‐doped carbon shells (Fe₃O₄/Fe₃C@NC) were prepared by directly pyrolyzing a mixture of Prussian blue (PB) and chitosan using a facile one‐step carbon‐bath route. The long‐term stability and methanol tolerance of the optimal catalyst were good and superior to those of commercial Pt/C (20 wt%). More importantly, the catalyst showed stronger ORR activities than Pt/C. We conclude that the high ORR activity of Fe₃O₄/Fe₃C@NC catalysts should be attributed to the synergetic effect between Fe₃C nanoparticles wrapped in carbon shells, which improves the activity of ORR and Fe₃O₄ nanoparticles neighbouring Fe‐N_x and significantly increases the number of active sites on the catalysts. Therefore, we believe that the one‐step carbon‐bath method provided in this work to synthesize highly active Fe‐based carbon materials as ORR catalysts is expected to be widely used in practical applications.