Wu, and nine other Chinese authors (2012) reported that coal, which is abundant and generally has an incompact structure, is a good candidate to replace graphite as the raw material for the production of graphene. In this paper, the authors described a solution-phase technique for the preparation of graphene from coal that they have developed. The precursor: graphene oxide from coal was examined by atomic force microscopy, dynamic light scattering and X-ray diffraction, the results showed the GO was a small and single layer sheet. The graphene was examined by X-ray photo-electron spectroscopy and Raman spectroscopy. Furthermore, graphene films have been prepared using direct solution process and the electrical conductivity and Hall effect have been studied. The results showed the conductivity of the films could reach as high as 2.5 × 105 Sm−1 and exhibited an n-type behavior.
Graphene has attracted world-wide attention after its discovery for its unique structure and a many useful properties in chemistry, physics and mechanics: the excellent electronic transport properties; the great strength and stiffness; and the good thermal conductivity. Large area sample preparation should be studied for applications or additional research. There are some methods to get graphene: micro-mechanical cleavage, some of which is not suitable for the large production. The growth on SiC wafer or other substrates, which can produce graphene with large area has the same problem with low output. Arc-discharge method is considered as a method for producing large-scale graphene sheets, but it is not easy to get single layer graphene. But, chemical exfoliation is an effective way of producing graphene in large quantity. However, it has a complicated process and requires time, and what’s more, great care should be taken in the use of KMnO4 and H2O2.
As indicated, coal may be a good candidate to replace graphite as the raw material of chemical exfoliation, for it is cheap and abundant. More importantly, coal is a molecular solid that has an incompact structure while graphite is a lattice solid without weak bonds, so the process can be simplified and some hazardous chemicals such as KMnO4 and H2O2 can be avoided. The authors report some details on the preparation of graphene from coal in large quantity by a new solution phase technique.
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