Noble‐Metal‐Promoted Three‐Dimensional Macroassembly of Single‐Layered Graphene Oxide

Abstract

The integration of nanostructured materials into macroscopic devices that can translate phenomena at the nanoscale to the macroscopic level has proved key to paving the way to realizing applications of nanomaterials. [1] To date, although remarkable progress has been made in the self-assembly of building blocks such as nanocrystals, nanotubes, nanowires, and the newly discovered graphenes, [2][3][4][5][6][7][8][9][10] very little success has been achieved with three-dimensional (3D) macroscale assemblies. Herein we report the controlled assembly of single-layered graphene oxide (GO) into 3D macrostructures promoted by a noble-metal nanocrystal (Au, Ag, Pd, Ir, Rh, or Pt, etc.). Although the density of such macroassemblies is very low (ca. 0.03 g cm À3 ), they have shown excellent mechanical properties, and have been utilized as fixed-bed catalysts for a Heck reaction resulting in both 100 % selectivity and conversion. We expect our endeavor may further the research and practical applications of graphene-based materials.Graphene is a well-defined two-dimensional structure of carbon atoms. It has received a great deal of attention because of its unique electronic, thermal, and mechanical properties. [11][12][13] Micromechanical cleavage from highly ordered pyrolytic graphite (HOPG) and the reduction of exfoliated graphite oxide sheets (graphene oxide, GO) are commonly used to produce graphene; [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] the reduction of GO appears to be a viable approach to the large-scale production of graphene. GO is usually prepared by oxidation of graphite powder with strong oxidants such as a mixture of concentrated sulfuric acid and potassium permanganate. The abundant oxygen-containing groups on GO endow it with excellent aqueous dispersion and make it easy to modify. [16][17][18][19][20][21][22][23][24][25] Recently, efforts have focused on the fabrication of graphene films through the self-assembly of the well-dispersed GO or functionalized graphene sheets. [20][21][22][23] Herein, we demonstrate that the 3D assembly of GO into macroscopic porous structures has been achieved successfully with the assistance of noble-metal nanocrystals (Au, Ag, Pd, Ir, Rh, Pt, etc.). The macroscopic size of the obtained samples can be easily controlled by adjusting the volume of the vessel, and the

Activation routes for high surface area graphene monoliths from graphene oxide colloids

“…9(c). The free standing monolith is really promising in the application fields such as catalysis [54,55], electrochemistry [56,57], sensors [58], energy storage [59] and environment technologies [60]. In this aspect, we need to design the robust graphene monolith of high surface area in future.…”

Graphene-based hybrid materials and their applications in energy storage and conversion

“…Hydro-or solvo-thermal process is a simple method for the preparation of graphene-based inorganic materials [4,25], in which GO could be reduced into graphene and the metal ions precursors would be transformed into metal or metal oxide species, therefore, the inorganic species could be incorporated into the graphene matrix. Novel metal and metal oxide nanoparticles promoted assembly of graphene with low density and tunable macro and microstructures are achieved successfully by using a hydrothermal method [26]. In a solvothermal reaction, graphene-CdS composite material with good structural and optoelectronic properties has been successfully and directly synthesized from the mixture of GO and Cd 2+ in the solvent of DMSO [21] (Figure 1).…”

Fabrication and characterization of graphene hydrogel via hydrothermal approach as a scaffold for preliminary study of cell growth

“…14 Recently, a number of researchers have investigated self-assembly of two-dimensional graphene oxide into threedimensional macrostructures. Various techniques have been employed to synthesize the three-dimensional macroscale architecture, such as easy one-step hydrothermal, 15 noble metal-promoted, 16 and divalent ion-promoted 17 self-assembly of graphene oxide via hydrothermal heating of a graphene oxide and DNA mixture, 18 mixing of graphene oxide and polyvinyl alcohol, 19 dispersion of graphene oxide in triblock copolymers, 20 and curing of graphene oxide with and without the presence of resorcinol-formaldehyde suspension. 21 The resulting three-dimensional graphene macroassembly has high mechanical strength, high thermal stability, a high surface area, high water content, good electrical conductivity, good electrochemical performance, good dye-loading capacity, and self-healing properties.…”