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

Summary

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.

Abstract

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.

Introduction

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, w....

Protocol

1. Resorcinol-formaldehyde (RF) Derived Graphene Aerogels

1. Na₂CO₃ catalyzed carbon aerogel (11% solids, cRF)
   1. 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.
   2. Add 37% formaldehyde solution (0.900 g, 11.4 mmol) to the resorcinol slurry and vortex for 1 min.
   3. Add sodium carbonate (0.003 g, 0.028 mmol) to the reaction mixture and vortex for 1 min.
   4. Transfer the reaction....

Results

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.......

Discussion

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.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Single Layer Graphene Oxide	Cheap Tubes	n/a	300-800 nm XY dimensions
single wall carbon nano tubes (SWCNTs)	Carbon Solutions	P2-SWNT
resorcinol	Aldrich	398047-500G
37% formaldehyde solution in water	Aldrich	252549
acetic acid	Aldrich	320099
ammonium hydroxide solution 28-30% NH3 basis	Aldrich	320145
sodium carbonate	Aldrich	791768
anthraquinone	Aldrich	a90004
Polaron supercritical dryer	Electron Microscopy Sciences	EMS 3100	this is a representative model, any critical point dryer compatible with acetone should work