Combustion heat of nitrogen-doped graphene nanoflakes studied by differential scanning calorimetry

Nitrogen-doped graphene nanoflakes (NGNFs) with variable N-doping level of 5.0–10.7 at.% were produced by chemical vapor deposition from different CH3CN/C6H6 mixtures. NGNFs were characterized by transmission electron microscopy, low-temperature nitrogen physisorption, X-ray photoelectron and Raman spectroscopies. Their combustion heats were measured by differential scanning calorimetry in the temperature range of 303–1273 K and showed a bell-shaped dependence on the nitrogen content with a maximum of 30.1 ± 1.0 kJ g−1 at a nitrogen level of 7.8 at.%. The contributions of the π–π stacking, resonance and surface/edge energies to the combustion heat were discussed. The approach for estimation of the combustion heat of NGNFs assuming the contributions from pyridinic, pyrrolic and graphitic nitrogen species was proposed for the first time.