Graphene[1] -a flat monolayer of carbon atoms tightly packed into a two-dimensional (2D) honeycomb lattice -is the basal building block in all graphitic materials. [2] Since it was first reported in 2004, [1] graphene has attracted great interest because of the unique electronic, [3][4][5][6][7][8][9][10] thermal, [11] and mechanical properties [12,13] arising from its strictly 2D structure, and to its potential technical applications. [2,[13][14][15][16] However, producing graphene on a large scale using existing mechanical methods is still unfeasible. Searching for alternative chemical approaches is an urgent matter. [17] However, the hydrophobic nature of graphene and its strong tendency to agglomerate in solvents [13] present a great challenge to the development of fabrication methods, and severely restrict its promising applications. Although the mechanism involved remains unproven, [18] the chemical reduction of readily available exfoliated graphite oxide (GO) with reducing agents such as hydrazine and dimethylhydrazine is a promising strategy in the large-scale production of graphene. [13,18,19] Unfortunately, the reducing agents involved are very hazardous, and the graphene obtained presents irreversibly agglomerated features in solvents that do not contain polymer surfactants.[13] Here, we report a new green route for the synthesis of processable graphene on a large scale. We observed that a stable graphene suspension could be quickly prepared by simply heating an exfoliated-GO suspension under strongly alkaline conditions at moderate temperatures (50-90 8C) (Figure 1a). Our initial purpose was to introduce functional groups to exfoliated GO by free-radical addition.[20] Surprisingly, the addition of NaOH to the GO suspension -to improve the solubility of the alkyl free-radical initiator, which is carboxyl-terminated -was accompanied by a fast, unexpected color change (from yellow-brown to homogeneous black). Careful experiments revealed that exfoliated GO can undergo fast deoxygenation in strongly alkaline solutions, resulting in stable aqueous graphene suspensions (Figure 1b). Typically, 150 mL of exfoliated-GO suspension (0.5-1 mL mg À1 ) and 1-2 mL NaOH or KOH solution (8 M) were loaded into a jacketed vessel, with hot water circulating through the outer chamber ( Figure 1S, Supporting Information). The temperature of the circulating water was constantly controlled by a temperature circulator, and the whole vessel was subjected to mild sonication (25 W, 40 KHz). The yellow-brown exfoliated-GO suspension became black after it was kept at the desired temperature (e.g. 80 8C) for a few minutes. The 13 C NMR spectrum of the GO (Figure 2a) confirms the presence of abundant epoxide and hydroxyl groups, [21] which should align perpendicular to the basal-plane carbon atoms. The carboxyl groups, which are located at the edges of the basal plane, are too few for 13 C NMR detection, in agreement with previous studies [21] on GO prepared by the Hummers method.[22] After the reaction, however, the exfoliated GO (...

Activation of reduced graphene oxide (RGO) using CO 2 to obtain highly porous and metal-free carbonaceous materials for adsorption and catalysis was investigated. The facile one-pot thermal process can simultaneously reduce graphene oxide and produce activated RGO without introducing any solid or aqueous activation agent. This process can significantly increase the specific surface area (SSA) of RGO from 200 to higher than 1200 m 2 /g, and the obtained materials were proven to be highly effective for adsorptive removal of both anionic (phenol) and cationic (methylene blue, MB) organics from water. Moreover, the activated RGO materials exhibited much better activity in effective activation of peroxymonosulfate (PMS) to produce sulfate radicals for oxidative degradation of MB.

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