From graphene oxide to pristine graphene: revealing the inner workings of the full structural restoration

Abstract

High temperature annealing is the only method known to date that allows the complete repair of a defective lattice of graphenes derived from graphite oxide, but most of the relevant aspects of such restoration processes are poorly understood. Here, we investigate both experimentally (scanning probe microscopy) and theoretically (molecular dynamics simulations) the thermal evolution of individual graphene oxide sheets, which is rationalized on the basis of the generation and the dynamics of atomic vacancies in the carbon lattice. For unreduced and mildly reduced graphene oxide sheets, the amount of generated vacancies was so large that they disintegrated at 1773-2073 K. By contrast, highly reduced sheets survived annealing and their structure could be completely restored at 2073 K. For the latter, a minor atomic-sized defect with six-fold symmetry was observed and ascribed to a stable cluster of nitrogen dopants. The thermal behavior of the sheets was significantly altered when they were supported on a vacancy-decorated graphite substrate, as well as for the overlapped/stacked sheets. In these cases, a net transfer of carbon atoms between neighboring sheets via atomic vacancies takes place, affording an additional healing process. Direct evidence of sheet coalescence with the step edge of the graphite substrate was also gathered from experiments and theory.

High quality, low oxygen content and biocompatible graphene nanosheets obtained by anodic exfoliation of different graphite types

“…As is well known from some chemically derived forms of graphene (i.e., GO and RGO) [9,[11][12][13]50], oxidation is usually associated to the introduction of a significant amount of defects and structural imperfections in the carbon lattice of graphene sheets, which in turn has an impact on such relevant properties as their electrical conductivity. The structural quality of the anodically exfoliated graphenes was evaluated by means of Raman spectroscopy, as illustrated in Fig.…”

“…Nevertheless, the obtained materials are typically very defective; as a result, many of the attractive physical properties observed in pristine graphene have been found to degrade in GO/RGO [11]. While full structural restoration of the latter has been shown to be feasible, the process relies on the use of very high temperatures (>1500°C), making it impractical for most applications [12,13]. Alternatively, defect-free graphene flakes can be procured by direct exfoliation of graphite in the liquid phase, usually with the assistance of ultrasound or shear forces [14][15][16].…”

Controlling the cooperative self-assembly of graphene oxide quantum dots in aqueous solutions

“…[1][2][3][4][5][6] The unique structure of monolayered graphene provides extraordinary electronic properties and excellent thermal and electrical conductivity. 12,13 The core of GO consists of small sp 2 hybridized 2D carbon domains that are surrounded by sp 3 hybridized carbon functionalized with carboxyl, epoxy and hydroxyl groups providing solubility in H 2 O. 12,13 The core of GO consists of small sp 2 hybridized 2D carbon domains that are surrounded by sp 3 hybridized carbon functionalized with carboxyl, epoxy and hydroxyl groups providing solubility in H 2 O.…”

Synergistic Effects of a Multifunctional Graphene Based Interlayer on Electrochemical Behavior and Structural Stability

“…A line scan across the edge of SG/Cu reveals a distinct step of approximately 0.4 nm, which is in good agreement with the thickness (0.34 nm) of the single graphene layer. [18][19][20] Contrastively, the topographic height profile of MG/Cu exhibits the edge of thin graphene layers with a step of ~3.8 nm, corresponding to the multi-layered graphene with approximately 10 layers. For further confirmation of the number and the uniformity of graphene layers, we performed Raman and UV-Vis spectroscopy analyses.…”