Preparation and Applications of Multidimensional Graphene Oxide-Based Materials

Abstract

Graphene is well known to have excellent electronic, mechanical and thermal properties, but it is still challenges to apply its intrinsic properties to real applications. One possible route to utilizing these properties for applications would be to incorporate graphene sheets in a composite material. Many approaches have been studied for the fabrication of graphene and graphene oxide (GO)-based composite materials with polymer, carbon nanomaterials and metal nanoparticles. This thesis is aimed at discussing the fabrication methods and applications of GO-based high performance composites. There have been many studies on GO-based composite materials, among which PVA has been considered as the most suitable polymer for GO-based composite applications. For various practical applications, it is very important to improve the mechanical properties of PVA. A large amount of oxygen-containing functional groups inserted onto the GO surface can form strong hydrogen bonds with the hydroxyl group of PVA. In this thesis, we have successfully fabricated PVA-GO composite films and fibers with improved mechanical strength by forming an additional adhesion properties from poly(dopamine) layers between the GO and PVA. The fabricated PVA/GO composite films and fibers resulted in increases in tensile modulus, ultimate tensile strength, and strain-to-failure. A combination of hydrogen bonding, strong adhesion of poly(dopamine) at the interface of PVA and GO sheets resulted in increases in tensile modulus, ultimate tensile strength, and strain-to-failure. In addition, the electrical conductivity of PVA/GO composite films and fibers can be restored owing to the partially reduced GO, and its application on humidity sensing and piezoresistive sensing will also be discussed. The excellent electrical properties and high specific surface area of graphene can provide a positive effect on various energy storage materials. However, the tendency to restack between sheets always remains to be solved. In this thesis, two-dimensional (2D) GO sheets were assembled into three-dimensional (3D) crumpled structure, and the effect of sheet morphology on electrochemical energy storage performances was studied. In order to prevent restacking of rGO sheets and ensure high specific surface area, crumpled and spherical structure of rGO, and CNT spacer insertion were also studied. Furthermore, we will discuss the fabrication of supercapacitor electrodes with superior performance by using porous rGO/CNT hybrids. Finally, the fabricated 3D porous rGO structure will be combined with platinum nanoparticles and applied as a electrocatalyst showing excellent performance in oxygen reduction reaction (ORR).