Edge-carboxylated graphene nanosheets via ball milling

Abstract

Low-cost, high-yield production of graphene nanosheets (GNs) is essential for practical applications. We have achieved high yield of edge-selectively carboxylated graphite (ECG) by a simple ball milling of pristine graphite in the presence of dry ice. The resultant ECG is highly dispersable in various solvents to self-exfoliate into single-and few-layer (≤5 layers) GNs. These stable ECG (or GN) dispersions have been used for solution processing, coupled with thermal decarboxylation, to produce large-area GN films for many potential applications ranging from electronic materials to chemical catalysts. The electrical conductivity of a thermally decarboxylated ECG film was found to be as high as 1214 S∕cm, which is superior to its GO counterparts. Ball milling can thus provide simple, but efficient and versatile, and eco-friendly (CO 2 -capturing) approaches to low-cost mass production of high-quality GNs for applications where GOs have been exploited and beyond.carbon dioxide | eco-friendly | edge-functionalization | graphite A s a building block for carbon nanomaterials of all other dimensionalities, such as 0D buckyball, 1D nanotubes, and 3D graphite, graphene nanosheets (GNs) with carbon atoms densely packed in a 2D honeycomb crystal lattice have recently attracted tremendous interest for various potential applications (1). Several techniques, including the peel-off by Scotch tape (2), epitaxial growth on SiC (3), chemical vapor deposition (CVD) (4, 5), and solution exfoliation of graphite oxide (GO) (6), have been reported for producing GNs. Although the Scotch tape method led to the Nobel-Prize-winning discovery of high quality GNs (2), it is unsuitable for large-area preparation of GN films due to technique difficulties. On the other hand, large-area thin GN films up to 30 in. have been prepared by CVD (7). However, the CVD process involves extremely careful fabrication processes, which appears to be too tedious and too expensive for mass production. The widely reported solution exfoliation of graphite into GO, followed by solution reduction (8-10), allows the mass production of GNs via an all-solution process. Due to strong interactions between the hexagonally sp 2 -bonded carbon layers in graphite, however, the solution exfoliation requires the involvement of hazardous strong oxidizing reagents (e.g., HNO 3 , KMnO 4 , and/or H 2 SO 4 ) and a tedious multistep process (8,9,11,12). Such a corrosive chemical oxidation often causes severe damage to the carbon basal plane to introduce a large number of chemical and topological defects (13). As a result, postexfoliation reduction of GO into reduced graphene oxide (rGO) is essential in order to restore the graphitic basal plane for the resultant GNs (6,[14][15][16][17][18][19]. To make the matter worse, the reduction reaction also involves hazardous reducing reagents (e.g., hydrazine, NaBH 4 ) with a limited reduction conversion (approximately 70%) (20). The reduced GO (rGO) still contains considerable oxygenated groups and structural defects, and thus additional...

Mechanochemical Functionalization of Carbon Black at Room Temperature

“…An alternative method that is prone to introduce functionalities and heteroatoms into a carbon network is based on mechanochemistry [23][24][25][26]. Due to the collision of milling balls inside a planetary ball mill, mechanical energies can be utilized to easily break and build chemical bonds [27].…”

Sulfur–Graphene Nanostructured Cathodes via Ball-Milling for High-Performance Lithium–Sulfur Batteries

“…S4b) for 0.7S-0.3GnP-700C -1M HCl clearly indicate that a considerable amount (3.8 at%, Table S2) of S-dopants have been strongly bonded into the carbon network through C-S (164.5 eV and 165.9 eV) and C-SO3 (168.3 eV) bonds, apart from those physically adsorbed sulfur. [39][40][41][42] . For all the S-GnPs, the intensity of the D band is higher than that of the G band due to the presence of defects induced by S-doping.…”

“…We have recently developed a simple low-cost, but effective and eco-friendly, ball-milling method for large-scale production of various graphene nanoplatelets (GnPs) edge-functionalized with different moieties without the basal plane damage, and hence good electrical/thermal conductivity [39][40][41][42] . Through the one-step ball-milling of graphite in the presence of sulfur (Fig.…”

Recent Progress on the Synthesis of Graphene-Based Nanostructures as Counter Electrodes in DSSCs Based on Iodine/Iodide Electrolytes

“…A simple, low-cost, and eco-friendly dry ball milling process was demonstrated to be effective for the decoration of various moieties onto the graphitic lattice [34]. The mechanochemical process was responsible for the dissociation of graphitic C-C bonds in exfoliated graphite flakes, creating carbon-based active species.…”