Graphene oxide and reduced graphene oxide studied by the XRD, TEM and electron spectroscopy methods

The commercial and synthesised few-layer graphene oxide, prepared using oxidation reactions, and few-layer reduced graphene oxide samples were structurally and chemically investigated by the X-ray diffraction (XRD), transmission electron microscopy (TEM) and electron spectroscopy methods, i.e. X-ray photoelectron spectroscopy (XPS) and reflection electron energy loss spectroscopy (REELS). The commercial graphene oxide (FL-GOc) shows a stacking nanostructure of about 22 x 6 nm average diameter by height with the distance of 0.9 nm between 6-7 graphene layers, whereas the respective reduced graphene oxide (FL-RGOc)-about 8 x 1 nm average diameter by height stacking nanostructure with the distance of 0.4 nm between 2-3 graphene layers (XRD). The REELS results are consistent with those by the XRD indicating 8 (FL-GOc) and 4 layers (FL-RGOc). In graphene oxide and reduced graphene oxide prepared from the graphite the REELS indicates 8-11 and 7-10 layers. All graphene oxide samples show the C/O ratio of 2.1-2.3, 26.5-32.1 at% of C sp(3) bonds and high content of functional oxygen groups (hydroxyl C-OH, epoxy-C-O-C, carbonyl-C=O, carboxyl-C-OOH, water) (XPS). Reduction increases the C/O ratio to 2.8-10.3, decreases C sp(3) content to 11.4-20.3 at% and also the content of C-O-C and C=O groups, accompanied by increasing content of C-OH and C-OOH groups. Formation of additional amount of water due to functional oxygen group reduction leads to layer delamination. Removing of functional oxygen groups and water molecules results in decreasing the distance between the graphene layers. (C) 2014 Published by Elsevier B.V.