Modification of Physicochemical Properties and Boosting Electrical Conductivity of Reduced Graphene Oxide Aerogels by Postsynthesis Treatment

Abstract

Electrically conductive graphene aerogels are attracting great interest as functional materials. Nevertheless, graphene aerogels synthesized from graphene oxide usually exhibit low electrical conductivity. In order to increase conductivity, herein a postsynthesis thermal treatment at several temperatures (from 300 to 1000 °C) has been applied to pristine reduced graphene oxide aerogels under two different atmospheres, namely, inert Ar flow and isopropanol+H 2 flow. Upon thermal treatment under Ar flow, the electrical conductivity of aerogel upscales with the treatment temperature. More remarkably, the electrical conductivity becomes 1 order of magnitude larger when the thermal treatment is carried out under isopropanol+H 2 instead of under Ar, while maintaining a very low density and porous structure. The electrical conductivity achieved is exceptionally high for such a lightweight and porous material. The exhaustive characterization allowed disclosing that the generation of carbon links between the reduced graphene oxide nanosheets is the reason for this enhancement. The electrically conductive aerogels have excellent prospects for application as scaffolds for energy storage or biomedical applications.

Direct Laser Writing of Poly(furfuryl Alcohol)/Graphene Oxide Electrodes for Electrochemical Determination of Ascorbic Acid

“…For the region from 2300 to 3300 cm −1 (second‐order), alongside with 2D, we fitted three more functions, described as G*, D+D’ and 2D’. The D* is associated to the disordered graphitic lattices from sp 2 ‐sp 3 bonds; the D’’ is related to amorphous phases; the D’ and D+D’ are associated to defective features of graphitic materials; and the G* comes from a process that involves the in‐plane transverse optical mode and longitudinal acoustic phonons [35–38] . The Raman spectrum of PFA/GO‐3.88 W and the respectively fitted functions are shown in Figure 2b, with similar spectra resolved for 3.76 and 4.0 W (Figure S4).…”

Waterborne Graphene- and Nanocellulose-Based Inks for Functional Conductive Films and 3D Structures

“…NCC seems to boost the GO hydrothermal reduction and the number of interparticle contacts, hence favoring the decrease in electrical resistance at the expense of aerogel density. In summary, it is possible to produce light and porous aerogels with a GO/CNT/NCC ternary system, with an anisotropic microstructure and fairly low electrical resistivity in the absence of any post-treatment, comparable to the ones with only GO [32]. As inferred from the SEM images (Figure 11), aerogels resulting from the unidirectional freeze-drying of hydrogels presented an anisotropic microstructure, with continuous straight pores parallel to the aerogel's longitudinal axis.…”

“…NCC seems to boost the GO hydrothermal reduction and the number of interparticle contacts, hence favoring the decrease in electrical resistance at the expense of aerogel density. In summary, it is possible to produce light and porous aerogels with a GO/CNT/NCC ternary system, with an anisotropic microstructure and fairly low electrical resistivity in the absence of any post-treatment, comparable to the ones with only GO [32].…”

“…Some of the working conditions led to porous and light graphene-based aerogels [26,28]. We have taken advantage of the possibilities granted by unidirectional freezing, followed by lyophilization, which are able to create an anisotropic internal microstructure composed of parallel channels, with critical applications in energy and environmental remediation [28,31,32]. In the present case, hydrogels were prepared under specific conditions and subjected to hydrothermal treatment with the ternary GO/NCC/CNT system in water (see Section 3.1 and Figure 10), and when subjected to unidirectional freezing prior to lyophilization, they also presented an anisotropic porous microstructure.…”

Mechanically Strong and Tailorable Polyimide Aerogels Prepared with Novel Silicone Polymer Crosslinkers

“…Aerogels are a class of nano-porous solid materials with high porosity, low density, high surface area, and low thermal conductivity [ 1 , 2 , 3 ]. Due to their unique properties, aerogels have been used in adsorption [ 4 , 5 ], catalysts, supercapacitors [ 6 , 7 ], sensors [ 8 ], energy storage [ 9 ], and so forth. Over the past few decades, aerogels made from polymer have been developed, such as phenol-formaldehyde resin [ 10 ], polyurethanes [ 11 ], polyureas [ 12 ], polyamides [ 13 ], and polyimide [ 14 ].…”