Structural Characterization of Commercial Graphite and Graphene Materials

Honeycomb hexagonal carbon atoms in graphite exist as crystalline hexagonal (2H) or rhombohedral (3R) phases. Carbon layers exist in an ABAB sequence in the commonly occurring 2H graphite structure with B layers shifted to a registered position relative to the A layers. The ABCABC stacking sequence in the 3R structure has C and B layers shifted by the same distance relative to the B and A layers, respectively [4]. Although highly ordered/ oriented graphite has a 2H hexagonal structure, a minor fraction of the 3R rhombohedral phase may remain in high-quality samples [5]. The discovery that the special allotrope of carbon, graphene, can be fabricated by using the scotch tape approach to produce a single layer of graphite, and the thinnestand strongest-known material universally, led to an increase in its popularity [6]. Graphene is often termed bi-, tri-, or few-layered (4 to 10 layers). Two-dimensional graphene consists of a sp2-hybridized carbon monolayered sheet network of densely packed rhombohedral-arranged honeycomb hexagonal crystal lattices and contains up to a dozen shells [7,8]. Graphene’s properties make it suitable in a variety of applications, such as batteries, sensors, structural composites, functional inks, electron emission displays, catalyst supports, in the biomedical field, and potentially in other future research fields [1-3,8-16].