Preparation of exfoliated graphite intercalated with nitrogen dioxide by direct gas-phase processing

• EG can be prepared from GIC by reaction of NO2 gas with NFG by a one-step method.
• The maximum EV of EG was up to 240 ml g−1 under the optimum conditions.
• Detailed investigations of GIC and EG were studied by SEM and TG–DSC–FTIR.
• NO2 gas could be recovered and recycled to avoid pollution and body injury.

Graphite intercalation compound (GIC) as a precursor of exfoliated graphite (EG) was easily prepared by direct reaction of nitrogen dioxide gas with natural flake graphite (NFG). This preparation involved a one-step method under optimum conditions of 55 °C and 0.45 MPa for 48 h in a dry, sealed steel container. The maximum exfoliation volume (EV) of EG was up to 240 ml g−1 with the exfoliated method at 1000 °C. A comparative study of properties and microstructure distinctions between GIC and EG samples was carried out using scanning electron microscopy, thermal gravity analysis, and differential scanning calorimetry coupled with Fourier transform infrared spectroscopy. The influence of reaction condition on the property, structure, and EV of the EG was also discussed.