Cobalt nitride nanoparticle-modified nitrogen-doped graphene aerogel used as an efficient catalyst for oxygen reduction reaction in acidic medium

Abstract

A promising cobalt nitride nanoparticle-modified nitrogen-doped graphene aerogel (CoN–NGA) has been prepared by chemical reduction and thermal treatment for oxygen reduction reaction (ORR). X-ray diffractometry result reveals the presence of cobalt nitride (CoN) nanoparticles on aerogel. X-ray photoelectron spectroscopy analyses reveal that nitrogen atoms have been doped into framework of graphene sheet and nitrogen-doped graphene sheets have been modified with cobalt nitride nanoparticles through CoN–C moieties. Analyses of scanning electron microscopy and Brunauer–Emmett–Teller show that CoN–NGA catalyst displays a various and interconnected pore structure. Because of a huge synergistic effect of the nitrogen-doped graphene, the three-dimensional porous structure and cobalt nitride nanoparticles, the prepared CoN–NGA catalyst displays comparable electrocatalytic activity and the similar onset potential as commercial Pt/C (20% loading). CoN–NGA catalyst exhibits superior stability and excellent methanol tolerance in acidic solution. Nitrogen-doped graphene has been provided positive potential and excellent methanol tolerance through functionalizing with cobalt nitride nanoparticles, because there are strong interactions between N-doped graphene and CoN nanoparticles through CoN–C moieties. It is found that CoN–C moieties are actual ORR active sites rather than CoN nanoparticles themselves. The possible mechanism of ORR on CoN–C moieties has been involved. This study demonstrates a feasible strategy to design non-precious metal nitride-modified heteroatom-doped graphene electrocatalyst for ORR in acidic electrolyte.