Hollow Nitrogen-Doped Carbon Spheres with Fe3O4 Nanoparticles Encapsulated as a Highly Active Oxygen-Reduction Catalyst.

The development of nonprecious electrocatalyst with low cost and high efficiency for the oxygen reduction reaction (ORR) is a main challenge for electrochemical energy technology. In this work, a hierarchical hollow core-shell structured N-doped carbon spheres (N-HSCS), in which Fe3O4 nanoparticles are encapsulated (Fe3O4/N-HCSC) has been successfully prepared. The Fe3O4/N-HCSC electrocatalyst exhibits a remarkable catalytic performance toward ORR. The porous hollow core-shell structure and synergistic effect between Fe3O4 and protective nitrogen-doped graphitic layers are mainly responsible for such an excellent ORR catalytic property and stability. This work demonstrates a promising strategy of nanostructure-engineering to the future design and preparation of highly efficient non-noble metal electrocatalysts.