Computationally Supported Neutron Scattering Study of Parent and Chemically Reduced Graphene Oxide

Abstract

Synthetic graphene oxide (GO) as well as the product of its reducing performed in the regime of hydrogenolysis (rGO) were studied by both elastic and inelastic neutron scattering at low and room temperature conditions. The neutron diffraction patterns were analyzed to confirm stacking structures of both species consisting of 2−3 and ∼7 layers of microsize lateral dimension and the interlayer distances of 7 and 3.5 Å, respectively. The inelastic incoherent neutron scattering spectra were analyzed in the frame of the computationally supported one-phonon amplitude-weighted density of vibrational states G(ω) approximation. Calculations of G(ω) spectra were performed in the framework of semilocal density functional theory. The computational models were adjusted to the atom mass content of both GO and rGO species. The presented study has revealed the retained water in the freshly made GO, corresponding to the relatively low humidity, which further reacts with the oxygen-containing groups at the GO basal planes. The reaction results in the formation of hydroxyls chemically bound to the GO core in the course of the prolong storage of the product under ambient conditions. The analysis of the rGO G(ω) spectrum has disclosed the chemical composition of its circumference attributing the latter to sets of CH units with a minor presence of atomic oxygen.

Parent and reduced graphene oxide of different origin in light of neutron scattering

“…4a for comparison. Since the relevant GO matrices of Ak-GO and ppGO are not hydrogen-rich and consist of carbon and oxygen atoms [3,4], their IINS spectra should be attributed primarily to confined water, whose G(ω) spectra are presented in Fig. 4c and d.…”

“…Graphene oxide and reduced graphene oxide have become the favorite species for neutron scattering study [1][2][3]. The hydrophilicity of GO and the hydrophobicity of rGO are responsible for the intense responses in both cases.…”

“…The hydrophilicity of GO and the hydrophobicity of rGO are responsible for the intense responses in both cases. The former is promoted by a considerable retaining of water between individual GO sheets as well as with hydroxyls that are formed during the interaction of the retained water with epoxy groups on the GO basal plane [3]. In the second case, the degree to which the rGO circumference is occupied with hydrogen depends on the rigour of the reduction conditions.…”

“…Both peaks are broadened, which gives evidence for a stacked structure with a relevant interlayer distance. The obtained data concerning the interlayer spacing in the studied samples, as well as the lateral dimension of the layer, are given in Table 2 (details of the NPD study analysis are given elsewhere [1][2][3][4]). As seen in the table, all the studied samples present graphite-like stacked structures differing therewith by both the number of layers in the relevant stacks and the lateral dimensions of the layers.…”

“…1 The definition > 20 nm marks the low limit of the lateral dimension of layers pointing that it is bigger than the coherent scattering region of crystalline graphite equal to ∼ 20 nm along c direction [9]. Actual layer dimensions are of microsize range [3,4]. …”