The effect of varying N/C ratios of nitrogen precursors during non-metal graphene catalyst synthesis

Nitrogen-doped carbon materials have great potential as metal-free catalysts in a variety of applications, including batteries, supercapacitors and fuel cells. In this paper, nitrogen-doped graphene (NG) catalysts were synthesized via thermal annealing with varying ratios of graphite oxide and melamine precursors. The NG catalysts were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The prepared NG catalysts were folded transparent films with wrinkles. The nitrogen content of the NG catalysts calculated from XPS varied from approximately 4.18%-7.40%. NG1 displayed the highest performance, with a remarkable reduction peak of 0.39 mA cm−2 at −0.21 V vs. Ag/AgCl in alkaline media. A direct correlation between total nitrogen content and catalytic activity was not observed, but catalytic activity was dependent on the nature of the nitrogen configurations. XPS analysis revealed that the high catalytic activity of NG1 is attributable to the configuration of the graphitic N-type nitrogen.