Nitrogen-doped carbon nanotube–graphene hybrid stabilizes MxN (M = Fe, Co) nanoparticles for efficient oxygen reduction reaction

A rationally designed CNT–GR hybrid support stabilizes selectively the small, nitrogen-rich phase of iron nitride nanoparticles and effectively incorporates nitrogen species into the carbon lattices to yield cost-effective and high-performance platinum group metal (PGM)-free catalysts for ORR. • Carbon nanotube–graphene hybrid support is rationally designed. • The support selectively yields small, nitrogen-rich iron nitride nanoparticles. • Oxygen reduction reaction performance is superior due to catalyst–support synergy. • This hybrid support is applicable to cobalt nitride catalysts. • The hybrid support will aid in designing high-performance platinum-free catalysts. A rationally designed carbon nanotube–graphene (CNT–GR) hybrid support stabilizes selectively the small, nitrogen-rich phase of iron nitride nanoparticles and incorporates effectively nitrogen species into the carbon lattices to yield cost-effective and high-performance platinum group metal (PGM)-free catalysts for the oxygen reduction reaction (ORR). This catalyst–support synergistic effect leads to superior ORR performance with a half-wave potential of 0.89 V vs. the reversible hydrogen electrode and superior durability against carbon corrosion and metal dissolution, compared to the independent use of CNTs and graphene as supports as well as Pt/C catalysts in alkaline media. This hybrid support is also applicable to cobalt nitride catalysts with the similar promotional effects. Therefore, our work explicitly reveals critical new roles of the CNT–GR hybrid material as an efficient support for developing strongly coupled and highly dispersed catalyst/support composites that could open up new avenues for use in a wide range of electrochemical and catalytic applications.