Kinetics of the defunctionalization of oxidized few-layer graphene nanoflakes

Abstract

Thermal defunctionalization of oxidized jellyfish-like few-layer graphene nanoflakes was studied under non-isothermal conditions by simultaneous thermal analysis. Activation energies for thermal decomposition of different oxygen functional groups were calculated by the Kissinger method and compared with those for oxidized carbon nanotubes. Oxygen content in graphene nanoflakes was found to significantly affect the decomposition activation energies of carboxylic and keto/hydroxy acids because of their acceptor properties and strong distortion of the graphene layers at the edges of the nanoflakes. The structure of the carbon material and the oxygen chemical state significantly influence the decomposition kinetics of thermally stable oxygen-containing groups. The activation energy for thermal decomposition of phenol groups (110-150 kJ mol) is close to that for graphene oxide reduction.

Structure and Property Evolution of Graphene Oxide Sheets during Low-Temperature Reduction on a Solid Substrate

“…The less data points for the GO suspensions stay only in the initial linear stage and change slower than the GO film, indicating a faster structure and opto-electronic property evolution on a solid than that in suspensions (Figure c). This is consistent with the result that the apparent activation energy obtained here is lower than those reported previously (134–167 kJ mol –1 ). ,, According to previous reports on thermal treatment of GO, extrinsic water plays an important role in C–C bond cleavage and functional group transformation, as interpreted by the proposed dynamic structural model. − Considering the humidity effects on SPFM imaging in our previous work, there is water adsorbed on the substrate surface or on the hydrophilic oxygen functional groups on GO. The functional groups are distributed on both sides of GO sheets.…”

“…This is consistent with the result that the apparent activation energy obtained here is lower than those reported previously (134−167 kJ mol −1 ). 42,46,49 According to previous reports on thermal treatment of GO, extrinsic water plays an important role in C−C bond cleavage and functional group transformation, as interpreted by the proposed dynamic structural model. 24−26 Considering the humidity effects on SPFM imaging in our previous work, 34 there is water adsorbed on the substrate surface or on the hydrophilic oxygen functional groups on GO.…”

“…41 The formation of sp 2 domains is rapid in the early stage (Figure 1c−g) and almost stable in the later stage (Figure 1h−j). This is probably because the activation energies for decomposition of varied functional groups are quite different, 42 especially some of them are too high to be removed at 100 °C. The average AHs gradually increase along with the heating time when the sp 2 domains recovered (Figure 1l).…”

New Composite Contrast Agents Based on Ln and Graphene Matrix for Multi-Energy Computed Tomography

“…The oxidation of GNFs was performed in the presence of HNO 3 (Chimmed, 70%, 1.4 g cm −3 density, and 99.999% purity) according to [ 30 ]. The GNFs were refluxed under HNO 3 for 1 h, filtered, washed with H 2 O, and dried at 80 °C for 24 h. The oxidized GNFs are referred to further as GNFs_ox.…”

A powder-metallurgy-based strategy toward three-dimensional graphene-like network for reinforcing copper matrix composites

“…Nevertheless, for reduced graphene oxide (RGO) nanosheets, which are the most common 2D graphene derivatives used as reinforcement, it is supposed that they have no way to directly bond together to form an integrated 3D network structure due to the limitation of the intermediate-temperature region for densification (500°C-1000°C). For the one thing, the temperature is far above the level that RGO nanosheets could be assembled by the Van Der Waals force and electrostatic repulsion benefited from the functional groups on their surface 20 . For another, the temperature is much lower than the level that the overlapped nanosheets fuse together through the high-temperature defect healing and carbon atomic rearrangement 21,22 .…”