Functional Viologens for Electrochemical Applications

Various viologen analogues were synthesized throughout the course of this doctoral work and targeted based on their electrochemical properties, stability, and solubility, and their role in energy storage and electrocatalysis was subsequently explored. Successful synthesis of each viologen was confirmed using Nuclear Magnetic Resonance (NMR) spectroscopy. Where possible, based on the stability of the molecules, electrochemical characterization was conducted. This included cyclic voltammetry (CV) and rotating disk electrode (RDE) studies which informed the decisions to pursue or abandon subsequent flow battery testing, and other applications.

This work describes a methodical approach to develop a sturdy, reliable, lab-scale rig for performance testing of Redox Flow Batteries, a potential long-term alternative for energy storage on both medium and large-scale applications. The design process and development involved systematically examining the construction and cell features and evaluating their benefits and drawbacks as to develop these technologies. Much research must be conducted on the lab scale to determine a range of performance metrics.

This work reports viologen electro-catalysts within a biphasic dichloromethane/ water system to achieve reductive dehalogenation of dihalides; a synthetically versatile route to substituted olefins in several industries including the pharmaceutical, fuel, and fine-chemical industry. The costs associated with these reactions are often exorbitant due to the use of superstoichiometric reductants, making this non-sustainable due to poor atom efficiency, and herein mediated electrosynthesis is used to develop a more efficient approach.

A range of 1,2-dibromo species are easily reduced using a simple undivided cell and inexpensive graphite electrodes in the first example of phase transfer electrocatalysis for these systems.

Beyond viologens, water-soluble flavin derivatives are potential redox actives species for redox flow batteries, based on their electrochemical stability and reversibility, and herein a sulphonate-functionalized flavin was characterized, which exhibited good redox properties in acidic aqueous electrolyte making it a strong candidate for an aqueous organic redox flow battery (AORFB).