Preparation, Structural Characterization, and Application of Reduced Graphene Oxide-Based Hybrid Materials

Abstract

Hybrid nanomaterials have the advantages of their individual components while also exhibiting new properties for practical applications. Many approaches have been studied for the synthesis of hybrid materials composed of metals, metal oxides, metal chalcogenides, polymers, and carbon materials. To apply these to practical applications such as field-effect transistors (FET), photovoltaic devices, and sensors, the synthesis of hybrid materials and fundamental study to understand their unexpected properties are very important. In addition, comprehension of the interaction at the interface between the two materials is needed. This paper discussed our approaches to develop new hybrid materials by means of functionalization. This thesis can be divided into two major parts for graphene-based hybrid materials: the functionalization of reduced graphene oxide (rGO) and rGO/TMD hybrid materials. The first part describes functionalization related to graphene oxide (GO) and rGO. Although these are the major applications of graphene, it is worth noting that graphene itself has a zero band-gap as well as chemical inertness, which weaken its competitive strength in the field of semiconductors and sensors. Therefore, tuning the electrical properties of graphene is important. Here, to control the electrical properties, the assembly of rGO and fullerene (C60) into hybrid (rGO/C60) wires was performed by π-π interaction between rGO and C60. Structural characterization and possible applications of the interaction between rGO and C60 will be discussed. In addition, amine-functionalized rGO, which has an n-doping effect in FET, is introduced. The mechanism of the doping effect and a facile method for the fabrication of rGO FET with self-assembled monolayers (SAMs) will also be discussed. The second part focuses on the synthesis of transition-metal dichalcogenide (TMD)-functionalized rGO and its electrocatalytic activity in the hydrogen evolution reaction (HER). Relatively, little is known about the synthesis of hybrid materials with TMD and rGO. In addition, the application of bulk TMDs for hydrogen evolution has been ignored for a long time owing to their poor activity. However, these materials, in particular 2D MoS2 and WS2 nanosheets, are starting to gain attention for use as catalysts in HER, alongside the explosive interest in graphene and other 2D materials. Therefore, synthesis of WS2/rGO hybrid sheets and their electrocatalytic activity levels have been demonstrated. Furthermore, we report the synthesis of a hybrid of CoS2/rGO, which has not been reported, and its electrocatalytic activity in HER.