Seminar: Hui-Ming Cheng
Professor and Head of the Advanced Carbon Division, Shenyang National Laboratory for Materials Science
Deputy Director, Institute for Metal Research, Chinese Academy of Sciences
Graphene, Graphene Networks and their Composites
April 22, 2011 | 11:00am | ESB 1001
Graphene, a unique two-dimensional carbon material, has many excellent properties, such as high specific surface area, good chemical stability, ultrahigh mobility, high electrical and thermal conductivity, as well as high mechanical strength and Young’s modulus. Therefore, graphene and its composite materials are expected to be used in many fields. This talk will focus on the synthesis and exploration of applications of graphene, graphene networks and their composite materials.
Graphene sheets with different numbers of layers  and large lateral sizes  were synthesized by chemical exfoliation and reduction. HI acid was used to efficiently reduce graphene oxide (GO) films , and the reduced GO films have high electrical conductivity and simultaneously maintain the integrity and flexibility of GO films. Based on chemically exfoliated graphene sheets, graphene-based hybrid materials were developed for electrochemical energy storage applications in lithium ion batteries and supercapacitors. It was found that synergetic effects between graphene sheets and metal oxides or conductive polymers can be used to develop energy storage materials with high capacity and capacitance, high rate capability and high cyclic performance. For example, graphene/polyaniline hybrid paper electrodes were prepared and showed a high tensile strength and large electrochemical capacitance, outperforming many other currently available carbon-based flexible electrodes . Graphene/hydrous RuO2  and MnO2  hybrid materials can be used in electrochemical capacitors with high energy density, and graphene-anchored Co3O4 , graphene-wrapped Fe3O4  and graphene/Li4Ti5O12 hybrids for lithium ion batteries were also developed.
Most recently, the direct synthesis of a three-dimensional foam-like graphene structure by CVD was realized, yielding materials known as graphene foams (GFs) . A GF consists of an interconnected network of graphene, which is flexible and offers fast transport channels for charge carriers, thus yielding high electrical and thermal conductivity. Even with a GF loading of as low as 0.5 wt %, GF/poly (dimethylsiloxane) (PDMS) composites exhibit a very high electrical conductivity of 10 S/cm, which is 6 orders of magnitude higher than chemically derived graphene-based materials. Using the unique network structure and outstanding electrical and mechanical properties of GFs, as an example, the great potential of GF/PDMS materials is demonstrated as flexible, foldable, and stretchable elastic conductors.