Stepwise isothermal thermogravimetric analysis allows the resolution of decomposition events that occur at neighbouring temperatures, by allowing each mass loss event to go to completion at a fixed temperature before subsequent temperature increment. In this work, we applied this technique to a sample of graphene oxide (GO) synthetised by our research group.
GO is a complex material containing multiple oxygenated groups on the surface of graphene flakes, each in a slightly different chemical environment. Conventional thermogravimetric analysis of GO carried out in nitrogen atmosphere evidences an important mass decomposition event taking place between around 120 and 220 °C. This temperature range corresponds to the decomposition of most of the oxygenated groups present on the surface of the carbon skeleton, which goes on to be slowly decomposed as the temperature increases.
The stepwise technique is able to resolve this event in three distinct events at 126, 150 and 178 °C respectively, and by interrupting the analysis after each of these steps, we were able to collect samples for chemical analysis, in order to determine which groups are decomposed at each temperature. These samples were analysed by X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy, which showed the evolution of the chemical composition of GO. We expect this technique to become relevant not only in the characterization of GO samples and other graphene derivatives, but also, for example, in the determination of which groups participate in functionalisation reactions, for example.