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...

Exploration of electrocatalysts for clean and sustainable hydrogen generation from water splitting has received huge attention due to the depletion of fossil fuels and environmental pollution.

“Pristine” graphite is edge-selectively functionalized with 4-aminobenzoic acid by a “direct” Friedel–Crafts acylation reaction in a polyphosphoric acid/phosphorus pentoxide medium to produce 4-aminobenzoyl edge-functionalized graphite (EFG). The EFG is readily dispersible in N-methyl-2-pyrrolidone (NMP). Subsequent solution casting leads to the formation of large-area graphene film on a silicon wafer. The film shows sheet resistances of 60 and 200 Ω/sq, respectively, before and after heat treatment at 900 °C in an argon atmosphere. Upon the heat treatment, the EFG film becomes a N-doped graphene (N-graphene) film to display outstanding electrocatalytic activity for oxygen reduction reaction (ORR).

Although there are a variety of methods for producing graphene, commercialization remains challenging because each method has its own pros and cons. For the wide use of graphene as a next generation material in diverse applications, the process by which graphene is manufactured must be robust enough to overcome barriers to commercialization, as has been experienced in commercializing carbon nanotube products. Here, a recent discovery of a new manufacturing process for effi cient delamination of graphite into graphene nanoplatelets (GnPs) via mechanochemical ball-milling is summarized. In this process, transferring suffi cient kinetic energy to graphitic frameworks will crack graphitic C-C bonds, generate active carbon species (mostly carbon free radicals), introduce edge-functional groups, and delaminate graphitic layers into edge-functionalized GnPs (EFGnPs). While this process is a method for mass production, it does not involve hazardous chemicals (e.g., corrosive acids and toxic reducing agents) such as those used for producing graphene oxide (GO) and reduced graphene oxide (rGO). Owing to its edgeselective functionalization, the EFGnPs have minimal basal area defects with selectivity of a variety of edge groups by forming edge C-X bonds (X = nonmetals or metalloids) that are tunable.ball-milling generates enough kinetic energy to crack graphitic C-C bonds, to induce edge reaction, to delaminate graphitic layers, and thus to yield edge-selectively functionalized graphene nanoplatelets (EFGnPs). Large quantities of EFGnPs could be effi ciently prepared by mechanochemical ball-milling. Due to the minimal distortion of the graphitic basal area, EFGnPs have high crystallinity and show excellent performance in a number of applications (e.g., fuel cells, [26][27][28][29][30][31] solar cells, [32][33][34][35] Li-ion batteries, [ 32,36 ] and fl ame retardants. [ 37 ] In addition, a variety of functional groups and/or heteroatoms can be selectively introduced at the edges for different applications. Hence, this EFGnPs approach may thoroughly satisfy diverse demands and overcome previous obstacles to commercialization. We believe that this process could revitalize graphene research for practical applications (e.g., polymer composites, energy conversion and storage, fl ame retardants, conductive inks) and thus enable graphene to take an actual leading position as a nextgeneration material in future science and technology.

Edge-functionalized graphite (EFG) is prepared via a "direct" covalent attachment of organic molecular wedges. The EFG is dispersed in N-methyl-2-pyrrolidone with a concentration as high as 0.27 mg mL(-1), leading to high-yield exfoliation of the three-dimensional graphite into two-dimensional graphene-like sheets.

Heteroatom doping into the graphitic frameworks have been intensively studied for the development of metal-free electrocatalysts. However, the choice of heteroatoms is limited to non-metallic elements and heteroatom-doped graphitic materials do not satisfy commercial demands in terms of cost and stability. Here we realize doping semimetal antimony (Sb) at the edges of graphene nanoplatelets (GnPs) via a simple mechanochemical reaction between pristine graphite and solid Sb. The covalent bonding of the metalloid Sb with the graphitic carbon is visualized using atomic-resolution transmission electron microscopy. The Sb-doped GnPs display zero loss of electrocatalytic activity for oxygen reduction reaction even after 100,000 cycles. Density functional theory calculations indicate that the multiple oxidation states (Sb3+ and Sb5+) of Sb are responsible for the unusual electrochemical stability. Sb-doped GnPs may provide new insights and practical methods for designing stable carbon-based electrocatalysts.

Hydrogen is considered af uture energy carrier that could improve energy storageo fi ntermittent solar/ wind power to solve energy and environmental problems. Based on such demand, development of electrocatalysts for hydrogen generation has been actively pursued. Although Pt is the most efficient catalyst for the hydrogen evolution reaction (HER), it hasl imits for widespread application, mainly its low abundance and high cost. Thus, developing an efficient catalyst from non-preciousm etals that are abun-dant and inexpensive remains an important challenge to replacemento fP t. Transition metals have been considered possible candidatest or eplace Pt-based catalysts. In this review,a mong the transition metals, we focus on recently developedm olybdenum-carbon( Mo-C)h ybrid materials as electrocatalysts for HER. In particular,t he synthesis strategy for Mo-C hybrid electrocatalysts and the role of various carbon nanocomposites in Mo-C hybrid systems are highlighted.[a] Dr.

We report in situ 'direct' grafting of dendritic macromolecular wedges to the edges of 'pristine' graphite. Because of the three-dimensional molecular architectures, the solubility of dendritic macromolecules is profoundly improved compared with that of their linear analogues. As a result, the resultant macromolecular wedge grafted graphite disperses well in common solvents. On the basis of results from wide-angle X-ray diffraction (WAXD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM), HPEK is selectively grafted at the edges of graphite. For the efficient delamination of graphite into graphene and graphene-like platelets, the dendritic macromolecules with numerous polar periphery groups not only acts as macromolecular wedges but provides chemical affinity to solvents.