This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. IM release LLNL-JRNL-667016.

1. Resorcinol-formaldehyde (RF) Derived Graphene Aerogels
<ol>
	<li>Na2CO3 catalyzed carbon aerogel (11% solids, cRF)
	<ol>
		<li>In a 40 ml scintillation vial, add deionized water (7.1 ml) to resorcinol (0.625 g, 5.68 mmol) and mix on a vortex for 1 min. Crush large resorcinol pieces to powder using a mortar and pestle prior to water addition. Note that they may not completely dissolve until the next step.</li>
		<li>Add 37% formaldehyde solution (0.900 g, 11.4 mmol) to the resorcinol slurry and ...

<ol>
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It is important to note that the procedures outlined here are only representative. Many adjustments are possible to tune materials for a specific application. For example, varying the starting material concentrations, while keeping resorcinol/formaldehyde (RF) ratio constant, can have an impact on the final material density. Catalyst loading can alter pore morphology, as a higher loading in the RF procedure leads to smaller primary particles and vice-versa. Activation time can play a role as well; at shorter activation t...

Since the isolation of graphene in 2004,1 interest in harnessing its unique properties has led to intense effort directed toward assembling graphene into three-dimensional, monolithic structures that retain the properties of individual graphene sheets.2-5 These efforts have been hampered by the fact that graphene itself is expensive and time consuming to produce and tends to aggregate in solution, which limits the scalability of materials based on graphene building blocks. Additionally, graphene assemblies are typically comprised of physical cross-linking interactions (e.g., van der Walls forces) between the individual graphene sheets, which are much less conductive and mechanically robust than chemical bond cross-links. Lawrence Livermore National Laboratory has been involved in the development of novel porous, low-density carbon materials since the 1980s.6 Several strategies have been identified to fabricate mass-producible graphene-based monolithic bulk materials from both low-cost polymer-derived carbon foams, which are called graphene aerogels (GAs),7 as well as by direct cross-linking of graphene oxide (GO) sheets, which are called graphene macro-assemblies (GMAs).8,9 These ultrahigh surface area bulk materials have high electrical and thermal conductivities, exceptional mechanical strength and elasticity, and tunable pore morphologies. GAs and GMAs have found utility in numerous applications including electrode materials in supercapacitors and rechargeable batteries, advanced catalyst supports, adsorbents, thermal insulation, sensors, and desalinization.10
The synthesis of graphene aerogels begins with sol-gel polymerization of an aqueous solution of resorcinol and formaldehyde to generate highly cross-linked organic gels. These gels are washed with water and acetone, then dried using supercritical CO2 and pyrolyzed in an inert atmosphere to give carbon aerogels with relatively low surface area and pore volume. Carbon aerogels are activated by controlled removal of carbon atoms under mild oxidizing condition (e.g., CO2) to form a cross-linked material composed of both amorphous carbon and graphite nanoplatelets, with higher surface area and open pore morphology.7 A unique advantage of the sol-gel synthesis is that GAs can be fabricated in a variety of forms, including monoliths and thin films, depending on the needs of the application. Carbon nanotubes11 and/or graphene sheets12 can be integrated into GAs by including these additives in the sol-gel precursor solution. This generates composite structures in which the additive becomes a part of the primary carbon network structure. Additionally, the GA framework can be functionalized after carbonization/activation either through modification of the aerogel surface or through the deposition of materials, for example catalyst nanoparticles, onto the framework structure.13
Graphene macro-assemblies (GMAs) are prepared by directly cross-linking suspended graphene oxide (GO) sheets, taking advantage of their inherent chemical functionality.9 GO sheets contain a variety of functional groups, including epoxide and hydroxide moieties, that can serve as chemical cross-linking sites. As in the GA preparation, assembled GMAs are supercritically dried to preserve the porous network, then pyrolized to reduce the chemical cross-links into conductive carbon bridges that provide structural support for the assembly. Due to the covalent carbon bridges between graphene sheets, GMAs have electrical conductivities and mechanical stiffness that are orders of magnitude higher than graphene assemblies formed with physical cross-linking. Additionally, GMAs have surface areas approaching the theoretical value of a single graphene sheet. Post-synthetic thermal treatment at elevated temperatures (&#62;1,050 &#176;C) can significantly improve the crystallinity of GMAs, leading to even higher conductivities and Young&#8217;s moduli as well as better thermal oxidation resistance.14 Post-synthetic chemical treatment of GMAs with redox-active organic molecules such as anthraquinone can enhance charge storage capacity in supercapacitor applications.15
The tunable material properties of GAs and GMAs are, in part, a result of carefully varying synthetic conditions such as reagent and catalyst concentrations, cure time and temperature, drying conditions, and carbonization/activation processes.16 This detailed video protocol aims to resolve ambiguities in the published methods, and to guide researchers attempting to reproduce the materials and conditions.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>Single Layer Graphene Oxide</td>
			<td>Cheap Tubes</td>
			<td>n/a</td>
			<td>300-800nm XY dimensions</td>
		</tr>
		<tr>
			<td>single wall carbon nano tubes (SWCNTs)</td>
			<td>Carbon Solutions</td>
			<td>P2-SWNT</td>
			<td></td>
		</tr>
		<tr>
			<td>resorcinol</td>
			<td>aldrich</td>
			<td>398047-500G</td>
			<td></td>
		</tr>
		<tr>
			<td>37% formaldehyde solution in water</td>
			<td>aldrich</td>
			<td>252549</td>
			<td></td>
		</tr>
		<tr>
			<td>acetic acid</td>
			<td>aldrich</td>
			<td>320099</td>
			<td></td>
		</tr>
		<tr>
			<td>ammonium hydroxide solution 28-30% NH3 basis</td>
			<td>aldrich</td>
			<td>320145</td>
			<td></td>
		</tr>
		<tr>
			<td>sodium carbonate</td>
			<td>aldrich</td>
			<td>791768</td>
			<td></td>
		</tr>
		<tr>
			<td>anthraquinone</td>
			<td>aldrich</td>
			<td>a90004</td>
			<td></td>
		</tr>
		<tr>
			<td>Polaron supercritical dryer</td>
			<td>Electron Microscopy Sciences</td>
			<td>EMS 3100</td>
			<td>this is a representative model, any critical point dryer compatible with acetone should work</td>
		</tr>
	</tbody>
</table>

synthesis and functionalization of 3d nano-graphene materials: graphene aerogels and graphene macro assemblies

Efforts to assemble graphene into three-dimensional monolithic structures have been hampered by the high cost and poor processability of graphene. Additionally, most reported graphene assemblies are held together through physical interactions (e.g., van der Waals forces) rather than chemical bonds, which limit their mechanical strength and conductivity. This video method details recently developed strategies to fabricate mass-producible, graphene-based bulk materials derived from either polymer foams or single layer graphene oxide. These materials consist primarily of individual graphene sheets connected through covalently bound carbon linkers. They maintain the favorable properties of graphene such as high surface area and high electrical and thermal conductivity, combined with tunable pore morphology and exceptional mechanical strength and elasticity. This flexible synthetic method can be extended to the fabrication of polymer/carbon nanotube (CNT) and polymer/graphene oxide (GO) composite materials. Furthermore, additional post-synthetic functionalization with anthraquinone is described, which enables a dramatic increase in charge storage performance in supercapacitor applications.

The evolution of material composition and morphology during fabrication can be tracked in various ways including X-ray diffraction, Raman and NMR spectroscopy, electron microscopy, and porosimetry. For example, in the synthesis, pyrolysis, and CO2 activation of GAs, the conversion was followed by X-ray diffraction (XRD) (Figure 1E). The absence of the stacking-related (002) diffraction peak in the XRD pattern after activation (blue trace) indicates the transition from a structure containing gr...

Watch this Scientific Journal Video about Synthesis and Functionalization of 3D Nano-graphene Materials: Graphene Aerogels and Graphene Macro Assemblies at JoVE.com

Synthesis and Functionalization of 3D Nano-graphene Materials: Graphene Aerogels and Graphene Macro Assemblies

This video method describes the synthesis of high surface area, monolithic 3D graphene-based materials derived from polymer precursors as well as single layer graphene oxide.

Efforts to assemble graphene into three-dimensional monolithic structures have been hampered by the high cost and poor processability of graphene. ...

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14.0K vues.  Lawrence Livermore National Laboratory. This video method describes the synthesis of high surface area, monolithic 3D graphene-based materials derived from polymer precursors as well as single layer graphene oxide.