Simultaneous reduction and N-doping of graphene oxides by low-energy N2+ ion sputtering

An easy and catalyst-free method was used to obtain N-doped reduced graphene oxides (N-RGO) through low-energy N2+ ion sputtering of graphene oxides (GO). The simultaneous reduction and N-doping of GO during the sputtering were systematically investigated by X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure and Raman spectroscopy. The N-doping and reduction levels, which are determined by the N/C and O/C atomic ratios from the quantitative XPS analysis, respectively, can be easily controlled by varying the N2+ ion sputtering time. In addition, three different N species, namely, nitrile-like N, graphitic N and pyridinic N, can be distinguished in N-RGO.