Spectroscopic analysis of mass-scale prepared GO and rGO from vein graphite through compositional improvement

Graphene oxide (GO) and reduced graphene oxide (rGO) were prepared from high pure Sri Lankan vein graphite on a lab-scale as well as on a mass scale following an improved Hummer’s method and a thermal method with a goal of investigating the quality of final products. Both oxidation and reduction process in mass scale production process have been subjected to composition and condition change considering factors such as safety, cost-effectiveness, eco-friendliness, user friendliness, and waste disposal management. Raman, XPS, FTIR, XRD, SEM, and TEM spectroscopic analysis were conducted to verify the final products on oxidation of graphite and its successive reduction. Exfoliation of graphite layers into few-layer rGO with large lateral size (D50, ca. 45 m) is visible through TEM and SEM. The XRD, FTIR, and XPS analysis indicated that the graphite was successfully oxidized to GO and reduced back to rGO with fewer oxygen functionalities, equivalent to ca. 7 % wt. The C/O ratio in XPS reflects that the oxygen-containing moieties are twice as rich in GO compared to graphite. XPS and FTIR further revealed epoxide and carboxylic groups being the main oxidized products of GO. Raman spectra further verified the restoration of sp2 hybridized bonds on the reduction of GO. The rGO prepared at 1000 ºC showed rGO with high conductivity, high surface area, fewest oxygen functions and fewest defects than reported. The combination of spectroscopic analysis carried out in the investigation provided valuable information and knowledge on the chemically produced graphene like rGO on mass scale with good properties compared to similar studies. The study demonstrates directions for further improvement of the synthesis method exploring the ability to use naturally pure vein graphite towards quality graphene on a mass scale.