Tailor-fitted preparation of chemically derived graphene-based materials and their specific applications

Abstract

As a dream material, graphene has attracted much attention because of its unique and outstanding properties such as optical transparency, lightness, high surface area, high mechanical strength, and ultrahigh electrical conductivity beyond existing materials. In particular, chemically derived graphene (CDG) has been widely studied because it is produced in large scale and easily processed using graphene oxide (GO) as a versatile platform. To produce CDG-based material with desired properties, modification of GO such as reduction, functionalization, doping, and decoration is necessary. Although a number of studies have covered preparation of CDG through various modifications and applications, they still do not exhibit the superb properties of graphene as expected. This is because the application-targeting design of CDG for maximizing performance by tackling underlying challenge has been rarely attempted. To address this issue, this thesis determines the required properties for target application and designs the CDG-based material by modifying GO to have an optimized material characteristics based on the requirements. Additionally, this thesis verifies the improved performances of tailor-fitted CDG-based materials in target applications. Part I introduces an overview of the synthesis, characteristics, and applications of CDG-based materials as well as research on representative modification methods of GO to produce CDG-based materials for various applications. In particular, it focuses on three main application fields: transparent conductive film (TCF), gas barrier layer (GBL), and hydrogen storage. This thesis investigated the key issues in each application and assessed the efforts undertaken in state of the art to solve challenges. Application-specific tailoring strategies for CDG-based materials in each application are suggested to address the limitations in previous research. Part II explains the tailor-fitted preparation method for CDG-based materials according to the strategies mentioned in Part I. Oxidation, reduction, and doping are used to produce CDG for TCF applications. As a tailor-fitted reducing agent for TCF, lithium naphthalenide (LN) is utilized since it derives ultrafast reduction of GO at room temperature without damaging the film and simultaneously provides a doping effect. As a result, CDG produced by LN reduction shows good TCF performance and stability. Functionalization with diol and reduction are used to prepare CDG for GBL applications. Edge-to-edge crosslinking functionalization, an unprecedented method for GBLs, induces an increased CDG lateral size, resulting in improved moisture shielding property. For hydrogen storage application, simultaneous reduction and functionalization of GO with polydopamine (PD) together with decoration of platinum (Pt) are used to synthesize CDG. The size, distribution, and loading amount of Pt and surface area of PD-functionalized CDG are tailored due to the systematic control of PD loading. As a result, the high hydrogen storage capacity even at room temperature is achieved. Part III summarizes the tailor-fitted design of CDG-based materials for TCF, GBL, and hydrogen storage applications and their performances. In conclusion, this thesis provides a CDG-based material preparation method through optimized modifications to improve performances in specific application, overcoming limitations of previous approaches.