Ultrafine Fe nanoparticles embedded in N-doped carbon nanotubes derived from highly dispersed g-C3N4 nanofibers for the oxygen reduction reaction

Abstract

Exploring non-noble-metal electrocatalysts is vital and challenging for promoting the oxygen reduction reaction (ORR) in energy conversion devices. In this work, N-doped carbon nanotubes derived from hydrolyzed graphitic carbon nitride (h-CN) wrapped Fe nanoparticles with core–shell nanostructures grafted on carbon nanotubes (Fe@h-CN/CNT) were obtained by a simple process. After the pretreatment, the introduced hydrophilic groups can improve the dispersibility of graphitic carbon nitride in water. Compared with its analogue prepared by untreated carbon nitride, Fe@h-CN/CNT exhibits a higher specific surface area and has more graphitic N for Fe–N_x coordination and more pyridinic N facilitating the four-electron pathway. In addition, the CNT network structure increases the conductivity of the Fe@h-CN/CNT composite electrocatalyst. As a result, our composite electrocatalyst shows desirable ORR performances with outstanding limited current density, comparable to commercial Pt/C in alkaline electrolyte. This work reveals that the pretreatment of the carbon nitride may have a significant effect on the electrocatalytical performance and provide a facile method for developing non-noble metal ORR catalysts.