Effects of Stage, Intercalant Species and Expansion Technique on Exfoliation of Graphite Intercalation Compound into Graphene Sheets

Graphite is composed of a series of stacked parallel graphene layers bonded by weak van der Waals forces. Although the weak interactions that hold the graphene sheets together allow them to slide readily over each other, the numerous weak bonds make it difficult to separate the sheets. A graphene sheet is a two-dimensional platelet consisting of a few graphene layers with an overall thickness in nanometer scale. Graphene sheets can be obtained from intercalation and subsequent exfoliation of graphite. To realize the expansion and exfoliation behaviors of graphite, graphite intercalation compound (GIC) is produced using an electrochemical method and three important factors, namely stage structure of GIC, intercalant species and expansion techniques, are taken into account. Graphene sheets produced from a lower stage FeCl₃-GIC display the best exfoliation behavior in terms of specific surface area, total pore volume and expansion volume. Microwave irradiation gives rise to a more explosive expansion than heating in a furnace.