Anti‐Solvent Derived Non‐Stacked Reduced Graphene Oxide for High Performance Supercapacitors

Abstract

An anti-solvent for graphene oxide (GO), hexane, is introduced to increase the surface area and the pore volume of the non-stacked GO/reduced GO 3D structure and allows the formation of a highly crumpled non-stacked GO powder, which clearly shows ideal supercapacitor behavior.

Selective Liquid‐Phase Extraction of Carboxylate‐Rich Graphene Quantum Dots from Graphene Oxide Dispersions

“…Figure 3d shows the X-ray diffraction (XRD) patterns of the pristine GO and the CGQDs. After the extraction process, the diffraction peak for CGQDs becomes broader, which is attributed to the fact that their own chemical structures could effectively prevent the stacking of the layers, [17,19] which is coincided with the above-mentioned results. In other word, even though structural properties of GQDs were changed, due to the lower interaction between the small sized particles and the absence of any re-stacking of the CGQDs sheets to give a random d-spacing.…”

“…The supernatant GO can be separated by simple filtration, since the precipitated GO was aggregated because of their crumpled structures which are caused by addition of Hx and Ch. [17] Through our methodology, we successfully obtained carboxylic acid-rich GQDs (< 20 nm) with high concentration (3 mg/mL) of solution. However, dispersibility of GO in typical organic solvents (N-methyl-2-pyrrolidon (NMP), dimethylformamide (DMF), ethanol (EtOH) and other various solvents tested) is not controllable after mixing with Hx and Ch.…”

“…The ratio of CÀC and CÀO (I C-C /I C-O ) corresponds to 0.6, which is agreeable with the previous results and it is dependent oxidation reaction time and degree. [17,18] Interestingly, the CÀO-C and CÀO peaks in CGQDs disappeared (top), while C=O and COOH peaks (E B = 298.4 eV) emerged after selective extraction process. Such phenomenon can be explained by the fact that primarily DAA molecules are interacted with -COOH groups on CGQDs via hydrogen bonding, which 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 can affect the solubility of CGQDs even in co-solvent system.…”

“…In contrast, the large sized GO also has hydrogen bonds with DAA molecules, however it could be immersed because of gravity. [17] Thus, it shows predominant carboxylate-rich chemical structure after extraction from GO dispersion. For exploring the detailed chemical functionalities, GO and CGQDs were analyzed using FT-IR spectroscopy, as shown in Figure 3b.…”

Flexible free-standing graphene paper with interconnected porous structure for energy storage

“…The formation of the layered structure in graphene paper decreased the surface area, resulting in the poor performance. 48 For PG paper, its porous structure offers high surface area facilitating the easy ionic transportation and enhanced accessibility of electrolyte, thus lead to the high capacitance.…”