Fabrication of Fe3C nanoparticles encapsulated in undoped graphite carbon and their catalysis for oxygen reduction

In recent years, nitrogenous metallic-complex catalysts for oxygen reduction reaction (ORR) have been extensively reported, but the exact role of Fe3C in the catalytic process is not clear due to the interference of reactive sites such as FexN, NxC and Fe nanoparticles. In this work, a new type of pyrolysis catalyst Fe3C-core/C-shell (Fe3C/C) was designed using Fe2O3 nanospheres and bacterial cellulose (BC) as raw materials. The encased nitrogen-free carbide isolated from the electrolyte, promoting the graphitic layers to form after BC carbonization toward high ORR catalytic activity, and the graphitic layers protected the internal carbide which exhibited excellent ORR activity and stability in both acidic and alkaline media. The catalyst was a model system for understanding the ORR active site of such encapsulated catalysts without other element doping. The carbide-based catalyst and mechanism proposed in this work provided a new idea for the development of ORR catalyst.