Electroreduction of oxygen on nitrogen-doped graphene oxide supported silver nanoparticles

Nitrogen-doped graphene oxide supported silver nanoparticles (Ag/NGO) have been synthesised using three different methods. The prepared catalysts were studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and electrochemically tested for oxygen reduction reaction (ORR) in alkaline solution. The Ag/NGO catalysts prepared by borohydride reduction showed the least degree of nanoparticle agglomeration and the material which was prepared using ascorbic acid yielded the biggest Ag particles. XPS revealed that the nitrogen to carbon atomic ratio was about 0.07 and EDS mapping showed that nitrogen was uniformly distributed over the graphene. The ORR on all the Ag/NGO catalysts proceeded via 4-electron pathway yielding water while on the support material, N-doped graphene oxide, the number of electrons transferred per O2 molecule was lower than four. The mass activity of all Ag/NGO catalysts was determined to be at least twice higher than that of NGO.