Tunable Synthesis of Nitrogen Doped Graphene from Fluorographene under Mild Conditions
2020
Zaoralová, Dagmar | Hrubý, Vítĕzslav | Šedajová, Veronika | Mach, Radim | Kupka, Vojtĕch | Ugolotti, Juri | Bakandritsos, Aristides | Medved’, Miroslav | Otyepka, Michal
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.
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