Electrochemical analysis of porphyrin paddlewheel frameworks, manganese oxide inverse-opal nanosheets, and tungsten trioxide electrodeposited onto graphene electrodes

In general, electrochemistry is used to study problems at the interface of chemical and electrical systems. As stated by Bard and Faulkner in Electrochemical Methods: Fundamentals and Applications, the field of electrochemistry is very broad and encompasses many different phenomena including electrophoresis, corrosion, displays, and batteries, as well as technologies like the electroplating of metals. As will be described, electrochemical methods have been used to characterize, modify and gain information about three materials systems. Chapter one is a brief introduction to the dissertation. Chapter two details the study of porphyrin-based metal organic frameworks (MOFs) for their ability to electrocatalyze oxygen reduction. Due to slow reaction kinetics, oxygen reduction requires a catalyst. The porphyrin-based MOFs are promising candidates for such a catalyst as they are designed to prevent undesirable porphyrin-porphyrin interactions as well as µ-oxo dimer formation. A brief survey using cyclic voltammetry was done with further experimentation including rotating disk electrode voltammetry to gain mechanistic information. The results of these experiments were inconclusive as different experiments suggested two or four electron oxygen reduction mechanisms. Due to the contradictory data, further experimentation is necessary. Chapter three details the two-part synthesis of a manganese oxide inverse-opal (IO) framework. Manganese oxide is commonly found in metal-air batteries. This application benefits from high surface area. In this case, the goal of the project was to produce a high surface area manganese oxide IO framework through a templating approach. The manganese oxide IO framework was produced through thermal degradation of manganese salt that had been infiltrated between self-assembled polystyrene spheres. Next, electrochemical oxidation was used to form manganese oxide nanosheets upon the IO framework. The material was tested briefly for its ability to electrocatalyze oxygen reduction. Chapter four details the fabrication of tungsten trioxide (WO3) electrochromic devices made with graphene electrodes. Electrochromic devices have a number of applications, including smart windows. WO3 was electrodeposited onto graphene electrodes. These electrodes were analyzed in two- and three-electrode configurations in conjunction with ultraviolet-visible spectrophotometry in order to gain quantitative information about the WO3 film coloring performance. A brief conclusion to the dissertation is found in chapter five