Mechanistic studies and applications of oxygen activation for energy conversion and storage
Date
2022
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Publisher
University of Delaware
Abstract
This dissertation discusses the applications and mechanistic studies of oxygen activation in energy conversion and storage, specifically in a redox flow battery (RFB) system and a fuel cell system. Chapter 1 provides a brief introduction of redox flow batteries, in which the history, the state-of-the-art, and the criteria for an ideal RFB system are presented. Chapter 2 explores two highly soluble and scalable ferrocenyl derivatives, FcNCl and FcNHCl, as negolytes to couple with the oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) as posolyte. By testing via long cycling constant potential and constant current electrolyses, the Fc-air RFBs have established their capability as stable, inexpensive, and efficient electrical energy storage devices. Chapter 3 aims to improve the previous ferrocenes by modifying the cyclopentadienyl rings with electron donating groups. Fc8NHCl and PMFcNCl deliver RFBs with cell potentials above 1.0 V. Upon long cycling, Fc8NHCl has shown that it can deliver high round-trip energy efficiency without any decomposition over time. Chapter 4 introduces a non-precious metal alternative to Pt for activation of oxygen in ORR, Co[10-DMIC], which is the only unadorned, monomeric cobalt tetrapyrrole that could drive the production of H2O efficiently. Chapter 5 elucidates the unique mechanism followed by Co[10-DMIC] via cryogenic UV-visible spectroscopy and computational calculations. Chapter 6 extends on the [10-DMIC] scaffold, by substituting the dimethyl groups with diphenyl and methylphenyl groups, the new cobalt tetrapyrroles can switch their selectivies towards H2O2 production.
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Keywords
Cobalt tetrapyrrole, Ferrocene, Multielectron redox chemistry, Oxygen reduction reaction, Redox flow batteries