Redox flow batteries (RFBs) are large-scale energy storage systems that enable the use of intermittent renewable energy resources, such as solar and wind power, which may not always be available when energy is being consumed. Unlike other battery technologies, RFBs can store significant amounts of energy in fluids stored in large reservoirs that are then flowed through cells to insert (i.e. charge) or to extract energy (i.e. discharge) from the system. Aqueous flow batteries employing dissolved organic redox active compounds (materials that can pick up and give off electrons) might safely and inexpensively store and deliver large amounts of electrical energy. These materials are environmentally benign, inflammable, and can be designed for low-cost production through modern, large-scale chemical synthesis technologies. However, chemical stability currently limits their long-term use in energy storage installations. This research project addresses fundamental understanding of the charge-discharge energy properties and degradation pathways of these energy-storing materials. The fundamental knowledge gained will also contribute towards other redox-based chemical processes, CO2 capture technologies and other electron-transfer processes relevant to biology. The project also continues a relationship with Boston's Museum of Science on a partnership to provide interactive presentations and content on the theme of renewable energy and its use in our nation's economy.

This fundamental research project will explore the thermodynamic stability and electrochemical kinetics of small organic molecules such as quinones in aqueous electrolytes. The use application is to understand chemical and electrochemical degradation at a mechanistic level. In aqueous solutions, some quinones are known to undergo rapid and reversible two-electron reductions to hydroquinone; they form the basis for new RFB electrolytes with the potential for enhanced efficiency and reduced cost. However, even the best of these material systems experiences a slow loss of capacity that, in some cases, has been attributed to molecular degradation. The investigators have identified a number of degradation pathways including the formation of semiquinone radical intermediates from single-electron reduction and correlated these to permanent loss of cell performance. Furthermore, the PIs have observed dramatic changes in quinone electrochemical kinetics when dissolved in solutions of various pH electrolytes. This project is a cross-school collaboration between the Department of Chemistry and Chemical Biology and the School of Engineering and Applied Sciences. This research will investigate the influences of molecular structure, substituent groups, pH, oxidation state, and electrolyte salts on molecular thermodynamic stability and electrochemical kinetics for redox-active organic compounds. The team will synthesize new molecules designed to answer fundamental questions and will evaluate their thermodynamic and kinetic properties using specially designed electrochemical flow cells.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

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Harvard University
United States
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