Multiscale characterization of 13C-enriched fine-grained graphitic materials for chemical and electrochemical applications

Abstract

13C-enriched fine-grained graphitic material has been studied towards its potential for chemical and electrochemical applications. The structural and morphological modification of the material as results of pressure-assisted thermal treatment and gaseous BrF3 and/or Br2 room-temperature treatments has been investigated using a combination of the characterization tools: electron microscopy, Raman spectroscopy, X-ray diffraction, X-ray photoelectron and near edge X-ray absorption fine structure spectroscopy, solid state nuclear magnetic resonance (NMR) spectroscopy and magnetic susceptibility measurements. It has been found that the starting material represents graphitized carbon with oxygen containing defects. The evidence of distorted sp2 hybridization of carbon was found in the Raman and the 13C NMR spectra. Under high pressure and temperature, some initially open graphitic edges are coupled that causes decreasing specific surface area and mean in-plane size of crystallites, and, generally, a higher degree of disorder. The Br2 treatment improves the material structure due to removal of tiny graphitic flakes and oxygenated carbon groups. The use of BrF3 results, in addition, in partial fluorination of graphitic material. Electrochemical characteristics along with a high degree of 13C isotope enrichment enable the application of these graphitic materials in operando studies using methods sensitive to 13C isotope, such as NMR.