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 (...

Nanoporous nickel hydroxide (Ni(OH)2) thin film was grown on the surface of ultrathin-graphite foam (UGF) via a hydrothermal reaction. The resulting free-standing Ni(OH)2/UGF composite was used as the electrode in a supercapacitor without the need for addition of either binder or metal-based current collector. The highly conductive 3D UGF network facilitates electron transport and the porous Ni(OH)2 thin film structure shortens ion diffusion paths and facilitates the rapid migration of electrolyte ions. An asymmetric supercapacitor was also made and studied with Ni(OH)2/UGF as the positive electrode and activated microwave exfoliated graphite oxide ('a-MEGO') as the negative electrode. The highest power density of the fully packaged asymmetric cell (44.0 kW/kg) was much higher (2-27 times higher), while the energy density was comparable to or higher, than high-end commercially available supercapacitors. This asymmetric supercapacitor had a capacitance retention of 63.2% after 10,000 cycles.

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A Si/graphene composite is drop-casted on an ultrathin-graphite foam (UGF) with three dimensional conductive network. The Si/graphene/UGF composite presents excellent stability and relatively high overall capacity when tested as an anode for rechargeable lithium ion batteries.

Scientific interest in graphene as a catalyst and as a catalyst support in heterogeneous catalytic reactions has grown dramatically over the past several years. The present critical review summarizes the multiple roles of graphene in heterogeneous catalysis and highlights the influence of defects, heteroatom-containing functionalities, and graphene's two-dimensional structure on catalytic performance. We first discuss the role and advantages of graphene as a catalyst support, with emphasis on its interactions with the catalytic phases and the influence of mass transfer processes. We then clarify the origin of the intrinsic catalytic activity of graphene in heterogeneous catalytic reactions. Finally we suggest challenges and potential practical applications for graphene in industrial processes.