Design, Controlled Construction And Properties Of Graphene-based Novel Porous Carbon

Due to its unique atomic structure and properties, graphene has attracted muchattention since it was discovered in2004, motivating the fast development ofcarbonaceous nanomaterials science. The two-dimensional layered structure ofhexagonally boned carbon makes graphene a basic unit for various types of sp2carbons. Hence, served as the building block, graphene offers new opportunities torealize assembly of novel carbon nanostructures and even directly intothree-dimensional (3D) macroscopic assemblies with desired properties. Assembly ofgraphene sheets into3D macroscopic structures not only can explore nanoscaleproperties of graphene but also more novel advanced properties in macroforms, and itis believed to be an important route to realize practical applications of graphene. Onthe basis of3D graphene porous assembly starting from graphene oxide (GO), thisdissertation mainly focuses on the preparation of different novel porous carbon with3D graphene network by adjusting self-assembly process of GO and tuning themicrostructure of formed3D network, and the assembly of porous graphene hybridarchitectures from the point of structure design was also realized, their potentialapplications as adsorbents and energy storage materials were further investigated.Specifically, the dissertation includes three parts. First, we introduced a linearpolymer with abundant-OH groups (Poly (vinyl alcohol), PVA) into the hydrothermalassembly process of GO, and PVA may act as the linker of graphene sheets to reduceπ-π stacking of graphene and make more surface of individual graphene sheetsaccessible. The finally obtained3D hierarchical porous carbon possesses a relativelyhigh specific surface area and the3D interconnected graphene network together withunique spheroidal and hierarchical pore structure with macropore openings at thesurface, which allows fast ion and electron transport into the innermost micropores.And therefore the carbon shows potential versatile applications as a high-performanceadsorbent and energy storage material. Second, based on the different interactionbetween solvent and graphene sheets during different drying process, we proposed asimple but very effective way to produce a highly dense but porous carbon by anevaporation-induced drying of a graphene hydrogel. The keypoint of producing thiscarbon is the evaporation of water exerts a “pulling force” on the flexible graphenesheets and results in the shrinkage of the3D network constructed of interlinked graphene sheets, which only reduces the pore size with significantly improvement indensity and does not reduce the graphene surface area. The finally formed carbonbalances two seemingly incompatible characteristics: a porous microstructure and ahigh density, and therefore has a ultrahigh volumetric capacitance for electrochemicalcapacitors. The carbon also shows an excellent cyclability and a very good ratecapability, which can be attributed to the3D porous network of compactly interlinkedgraphene sheets with fast ion transport channel and acceptable electron conductivity.In addition，structure evolution of the carbon during thermal treatment process atdifferent temperatures has also been investigated. Third, based on3D graphene porousnetwork, all-carbon composites were prepared by hydrothermal co-assembly processand graphene/polyaniline composites were produce by static adsorption followed withsitu chemical polymerization method. The graphene/carbon nanotube hybrids withuniform distribution were selected for high oxygen reduction reaction activity. A layerof nano-polyaniline uniformly deposited on graphene sheets in composites whichshows high capacitance and excellent rate performance as electrode materials ofsupercapacitors.