Investigating The Chemical Properties Of Graphene Using Electrochemical Methods
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Graphene, a single layer of carbon atoms, has been in the center stage of materials research since its discovery in 2004. Its chemical properties are yet to be understood. In this dissertation, I will discuss the investigation of graphene's chemical properties using various electrochemical techniques. First, we found that the heterogeneous electron transfer rate of ferrocene at graphene is one order of magnitude higher than that of highly oriented pyrolytic graphite. The enhanced electrochemical reactivity is ascribed to the presence of corrugations and imperfections that disrupt the sp2 conjugation of graphene which can alter its electrical, chemical, and mechanical properties. We have further examined the rate of heterogeneous electron transfer of various redox mediators at graphene using scanning electrochemical microscopy (SECM). SECM offers a versatile set of tools to characterize the reactivity of surfaces with temporal and spatial resolution. It was found that the sites with a large concentration of defects are approximately one order of magnitude more reactive compared to more pristine graphene surfaces. Furthermore, the reactivity of graphene defects can be selectively passivated by carefully controlling the electropolymerization conditions of o-phenylenediamine. The use of spatially resolved scanning electrochemical microscopy for detecting the presence and the "healing" of defects on graphene provides a strategy for in situ characterization and control of this attractive surface, enabling optimization of its properties for application in electronics, sensing, and electrocatalysis.
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Ralph, Daniel C