Preparation Of Three-Dimensional Graphene Composites And Their Properties

Graphene has a very important application in nanometer material, biological engineering and fine chemical industry. It has unique physical and chemical properties and also used as catalyst carrier or three dimensional materials. Usually, when the two-dimensional graphene materials presence as powder, the specific surface area and their excellent thermal conductivity and electrical conductivity could be limited. So, the development of three-dimensional graphene skeleton as the main body of the composite material has important academic value and broad application prospects. Considering this, we designed and synthesised three-dimensional graphene/polymer composite materials, three-dimensional graphene/inorganic nanoparticles composites, and studyed their applications in the field of new functional materials, especially as a catalyst in the field of biomass conversion.In Chapter II, instead of adding graphene sheets to the polymer to increase the glass transition temperature (Tg) as usual, we combined three-dimensional graphene network with polymer network to create a new inorganic-organic material. The as-prepared rGO/PAA double network (DN) hydrogel shows both elasticity and electrical conductivity, it would stay unbroken after stretched to six times in length. At the same time, it has excellent ductility and response behavior to gases with different polarity. We believe it has potential application as a flexible conductive material for next generation of electric devices.In Chapter III, we did some exploration about preparation and processing control of graphene, using chemical oxidation reduction approach in the preparation of graphene aerogels. First, strong oxidizer and concentrated sulfuric acid was carried out on the flake graphite intercalating and hydrophilic group introducing to get graphene oxide. Afterwards we used vitamin C as the reducing agent to prepare graphene hydrogels. Aiming to improve electrochemical and material properties of three-dimensional graphene composites, we got different structures of graphene aerogels through different freeze-drying methods. We also tried to use emulsion shear method to prepare natural graphene layers, although the yield was limited even single or less layers of graphene films could be found. Finally, we combined high specific surface area of graphene and nanometer catalytic properties of Nb2O5, using graphene for catalyst carrier to regulate the wettability of catalyst. Much as we tried, we failed to get the expected result of catalytic fructose to 5-HMF. but we still hope it’s useful for catalyst design.Combining respective advantages of graphene and metal organic framework structure (MOF) materials, we designed and synthesised three-dimensional ZIF-8/RGO composite materials as catalyst. In Chapter IV, we used ZIF-8/RGO to catalyze the cellulose degradation and conversion in homogeneous solution. Because of the corrosion resistence of graphene and catalysis ability of ZIF-8, we selectively converted cellulose into small molecular compounds, such as formic acid, acetic acid and oxalic acid.We designed and synthesised the iron or chromium-based MOF and its complexes with three-dimensional graphene in Chapter V, exploring the influence of temperature, reaction time and different catalyst in fructose dehydration process. Usually, fructose would be dehydrated into 5-HMF, however, fructose can be selectively transformed to formic acid which is usually considered as a side effect in fructose dehydration process when using water as solvent and appropriate catalyst.