Oxidation of HSAG Graphites Using a Bruker D8 Advance Diffractometer
High surface area graphite (HSAG) samples were subjected to oxygen plasma treatment. The oxidation reaction of the oxygen plasma causes the etching of the graphitic structures. This oxidation process preferentially affects the first graphene layers. However, it also affects the aromatic network of the material.
In this study, the influence of the exposure time on the oxidation degree of graphitic samples was investigated. The oxidation level of G100, a HSAG sample, increased with increasing treatment time. A series of X-ray diffractograms were recorded using a Bruker D8 Advance diffractometer. They showed that the oxidation level of G100 sample increased after 10 min of exposure, while the G300 sample showed less oxidation.
The Raman spectra of the G100 sample showed an asymmetric profile similar to the doublet structure of HOPG. The Raman spectra of the G300 sample did not show a doublet structure. On the other hand, it showed a more asymmetric profile, which is likely due to the expanded graphene sheets.
An inset on the right side of the graph shows the intensity curves of the two peaks. These peaks are the asymmetrical aromatic sp2 structures. The asymmetry is accentuated with the longer treatment.
The asymmetry is probably a result of the larger particle size of the G300 sample. It is believed that the larger graphitic particles exhibit more disorder and oxidation. Because of this, blending in a proportion of smaller graphite particles can mitigate the inhomogeneous distribution of material and improve Coulombic efficiency.