Nitrogen-doped carbon nanoflowers with in situ generated Fe3C embedded carbon nanotubes for efficient oxygen reduction electrocatalysts

Abstract

Oxygen reduction reaction (ORR) electrocatalysts are important to promote large-scale practical applications of fuel cells because of their high activity, low cost, and high durability. Particularly, Fe-N co-doped graded porous carbon has proven to have a compelling prospect for ORR electrocatalysis. Herein, a simple and environmentally friendly method has been proposed to synthesize a novel nitrogen-doped carbon nanoflowers with in situ generated Fe3C embedded carbon nanotubes (Fe3C@NC) via the direct pyrolysis of Zn-Fe-ZIFs in a N2 atmosphere. The doping amount of Fe is the most critical factor for the formation of Fe3C active sites. The catalytic activity of oxygen reduction reaction (ORR) has been improved by the synergistic effect of Fe3C active sites and high content of pyridine N. The typical Fe3C@NC-60-800 material exhibits superior ORR performance of high onset potential (Eonest, 0.987 V) and half-wave potential (E1/2, 0.855 V), good stability and methanol tolerance, which notably outperforming the more costly commercial Pt/C catalysts. The presented synthesis strategy can provide new opportunities for the design and construction of metal-organic framework-derived nanomaterials with reasonable composition and required porous structures to enhance their electrocatalytic performance.