Synthesis, Characterization And Application Of Graphene Oxide-based And Graphene-based Composite Gel

This dissertation has illustrated the synthesis, characterization and application of novel 3D porous materials based on graphene oxide and graphene. By utilizing graphene oxide as the starting material, we have successfully synthesized graphene oxide/pyrrole-formaldehyde composite hydrogel via in situ polymerization of pyrrole and formaldehyde in the presence of graphene oxide sheets without additional catalyst. Moreover, graphene oxide/pyrrole-formaldehyde composite aerogels was obtained with subsequent freeze drying of above hydrogels. The structure properties and performance in gas adsorption of resulting gels were studied by a variety of characterization methods. In addition, N-doped graphene/sulfur composite porous material was successfully obtained based on hydrothermal produced N-doped graphene aerogel. The article also investigated the influences generated by sulfur to native N-doped graphene aerogel. The main research content and conclusions are shown as below:(1) By using pyrrole and formaldehyde monomers as starting materials, graphene oxide/pyrrole-formaldehyde composite hydrogel was successful synthesized via in situ polymerization of pyrrole and formaldehyde in the presence of graphene oxide sheets without additional catalyst. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, infrared spectroscopy, and Raman spectroscopy were used to comprehensively characterize the structures, compositions and morphologies of resultants. A series of control experiments demonstrated that graphene oxide can not only play as a template but also as a catalyst to promote the growth of polymer during the formation of gel.(2) After freeze drying of graphene oxide/pyrrole-formaldehyde composite hydrogel precursor, porous graphene oxide/pyrrole-formaldehyde composite aerogel was fabricated. Scanning electron microscopy confirmed its porosity. Pore structures were characterized by Nitrogen adsorption test and its BET surface areas was demonstrated to be 665 m2/g. In addition, gas adsorption application was conducted with composite aerogels containing different mixing ratio between GO and polymer. CO2 adsorption ability can reach up to 11.1% which indicated the potential of composite aerogel in gas adsorption application.(3) Finally, N-doped graphene/sulfur composite porous material was successfully obtained based on hydrothermal produced N-doped graphene aerogel. Heat treatment on the mixture of sulfur and N-doped graphene aerogel result in the permeating of sulfur into the pore of aerogel which promoted the formation of N-doped graphene/sulfur composite porous material. The variations in composition and porosity were studied by Scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, infrared spectroscopy, Raman spectroscopy and Nitrogen adsorption tests. This novel composite porous material shows great potential in the application of Li-Sulfur battery.