Unveiling a facile approach for large-scale synthesis of N-doped graphene with tuned electrical properties

Abstract

In this paper, we for the first time demonstrate efficient nitrogen doping of graphene oxide (GO) with nitrogen concentration of up to 5 at.% via modified Hummers' method. Using X-ray photoelectron spectroscopy (XPS), X-ray absorbance spectroscopy (XAS) and Fourier transform infrared spectroscopy (FTIR) techniques, we have found out graphitic nitrogen to be the dominant type of the implemented nitrogen species. At the same time, the subsequent GO thermal reduction to graphene appears to result in a transformation of the graphitic nitrogen into pyridines and pyrroles. The mechanisms of the observed GO nitrogen doping and conversion of the nitrogen species are proposed, providing an opportunity to control the type and concentration of the implemented nitrogen within the approach. A two-time increase of the graphenes' conductivity is observed due to the performed nitrogen doping. Further comprehensive electrical studies combined with the transmission electron microscopy (TEM) and density functional theory (DFT) modeling have allowed us to estimate the conductivity mechanism and the impact of the implemented nitrogen. As a net result, a simple method to synthesize N-doped graphene with the desired type of the nitrogen species is developed, which leads to new perspective applications for graphene, i.e. supercapacitors, catalysis, and sensors.