Investigation of the Pore Structure of Exfoliated Graphite Based on Highly Oriented Pyrolytic Graphite Nitrate

Abstract

Graphite intercalated compounds (GICs) with different stage numbers were prepared from highly oriented pyrolytic graphite (HOPG) and nitric acid using a chemical method. Exfoliated graphite (EG-T) was synthesized from GICs by water treatment followed by thermal shock. The effects of the graphite oxidation depth on the EG-T thermal expansion coefficient, volatile content, and total porosity were examined. However, the main purpose of this work was investigation of the dependence of the inner EG-T pore structure on the level of oxidation. Thus, we studied the micro- and mesopore structure and specific surface area by nitrogen porosimetry and the modern 2D-NLDFT method to calculate the pore size distribution and pore volume. As well, we performed a mercury porosimetry experiment to determine the macropore characteristics. We examined the pore space using a number of scanning electron micrographs of EG-T particle cross-sections using an image processing technique. In this way we showed the strong correlation between the EG-T pore structure parameters and oxidation depth of graphite.