Safety Implications for Explosive Mode Graphite Oxide Thermal Exfoliation

The high monolayer surface area (~2600 m²/g) of graphene and graphene oxide offers immense potential for use in catalysts, gas adsorption, gas storage, and separation applications. Unfortunately, this monolayer surface area is often lost during graphene oxide processing. Thermal reduction of graphite oxide (GO) is an important processing step in the fabrication of many graphene and graphene oxide-based materials.  It has been determined that GO is an ‘energetic’ material that decomposes to reduced GO. However, the magnitude of the exothermicity, the onset temperature for the thermal exfoliation reaction, and the factors affecting both those parameters remain unclear. Our work demonstrates that the average GO heat of decomposition is 1600 J/g and the reaction onset temperature is ~150 ^oC.  Depending on the conditions, thermal exfoliation of GO can proceed in an explosive mode while heated in inert atmosphere, introducing safety issues for storage in large scale. This work also demonstrates that the addition of interstitial hydroxide into GO lowers the onset temperature and total exothermicity of the reaction and could promote the explosive mode decomposition. It is also shown that a prior base treatment of GO lowers the explosion onset temperature to close to common drying conditions (~100 ^oC), while the addition of potassium (common combustion catalyst) and water have been shown not to affect the thermal runaway reaction significantly.  Our predictions of the incubation period for the self-heating of GO provide an indication of the appropriate safe storage temperature and shelf life for the material.  These conclusions are indicative of a resulting increased understanding of the factors affecting the explosion, bringing safe, large-scale storage and processing closer to reality.