Composition Regulation and Morphological Engineering of Fe/Fe3O4 Nanoparticle-Embedded N-Doped Carbon Nanotube with Improved Oxygen Reduction Reaction for Zinc-Air Batteries

The construction of high-performance and low-cost oxygen reduction electrocatalysts is crucial for the commercialization of zinc-air batteries (ZABs). One-dimensional (1D) carbon nanotubes have the advantage of an open structure that facilitates the diffusion of ions and reaction products and provides abundant active sites. In this work, a 1D Fe/Fe3O4-embedded N-doped carbon nanotube (Fe3O4/Fe–N–CNT) with high catalytic activity is prepared by a simple mechanical mixing and secondary calcination method. The Fe3O4/Fe–N–CNT with its unique 1D carbon nanotube structure and large specific surface area, facilitates electron transport and exposes more active centers. The interaction between Fe/Fe3O4 nanoparticles and the N-doped carbon material promotes the oxygen reduction reaction (ORR). The obtained Fe3O4/Fe–N–CNT catalyst has a high half-wave potential (E1/2 = 0.85 V vs RHE), which is significantly better than the Pt/C catalyst (E1/2 = 0.8253 V vs RHE). Meanwhile, the Fe3O4/Fe–N–CNT-assembled ZABs achieve a larger power density of 148 mW cm–2 than Pt/C based ZABs (110 mW cm–2), confirming its commercialization potential. These findings indicate that morphology and composition regulation are important in guiding the electrocatalytic performance of the catalysts.