Tunable Synthesis of Nitrogen Doped Graphene from Fluorographene under Mild Conditions

The nitrogen doping of graphene via mild and low energy processes to afford homogeneous product composition and topology with high nitrogen content (>10 at. %) remains a challenge of contemporary 2D materials chemistry. Here, we report a previously unexplored route to synthesize N-doped graphene (NG) with exceptionally high N content (up to 18.2 at. %) by reaction of fluorographene (FG) with NaNH2 in N,N-dimethylformamide (at 130 °C) or acetonitrile (at 70 °C). The N content can be tuned by changing the reaction time, temperature, and/or solvent, ranging from 6.6 to 18.2 at. %, mainly in the form of pyridinic and pyrrolic configurations. With thermal annealing, the N content remained constant up to 400 °C but then decreased by ∼50% upon being further annealed to 1000 °C. Density functional theory (DFT) calculations showed that nitrogen incorporation into the carbon lattice mostly occurred at vacancies present in the starting material. We also conducted a thorough rationalization of side-reaction pathways leading to byproducts, which were confirmed by GC-MS analysis. This is the highest yet recorded N content for a wet chemical doping procedure and at such a low temperature of 70 °C. The reported synthetic approach thus offers a sustainable and cost-effective way to prepare NG with a broad tunability window of N content for potential applications related to energy storage and catalysis