CAREER: Designer Redox Active Molecules for Sustainable Electrochemical Energy Storage

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In this NSF CAREER project, funded by the Chemical Structure, Dynamics & Mechanisms B Program of the Chemistry Division, Professor Tianbiao Liu of the Department of Chemistry and Biochemistry at Utah State University is developing low-cost, tunable, and well-defined redox active molecules for aqueous organic redox flow batteries (AORFBs). These flow batteries are useful for low-cost and more environmentally-friendly energy storage. The project focuses on the in-depth understanding of the structure and battery performance relationships of battery components. The new knowledge provides guidance in developing low-cost redox active molecules for the use of redox flow batteries as a environmentally-friendly and scalable energy storage platform, thus, alleviating the global reliance on fossil fuels and enhancing the sustainable development of our society. The project lies at the interface of organic, inorganic, materials, and electrochemistry, and is therefore well suited for the education of scientists at all levels. Professor Liu develops educational programs serving Utah Stat University and wider communities throughout the State of Utah. Students at all education levels participate in building the necessary talent pool of the next generation of scientists and engineers to work in the critically important and emerging field of renewable energy storage. Specifically, Professor Liu works with the USU Eastern Blanding Native American Summer Mentorship Program (NASMP) and the USU Stars Program. These programs focus on attracting and training native American students who are underrepresented in STEM disciplines and on stimulating interest and curiosity in science of academically-talented local high school students. Aqueous organic redox flow batteries (AORFBs) employing redox active organic molecules have been demonstrated to be highly attractive for energy storage. Previous studies of AORFBs have primarily emphasized full flow battery performance using redox active molecules. However, few studies have paid attention to the in-depth understanding of the correlation between physicochemical properties of individual redox active molecules and their battery performance. This project focuses on the molecular engineering and property studies of redox active viologens (anolyte), ferrocenes (catholyte) and 2,2,6,6-tetramethyl-1-piperidinyloxy molecules (catholyte), and their battery performance in AORFBs. These three classes of redox active molecules are investigated to answer the following questions: 1) How do the molecular structures of redox active molecules determine their physicochemical properties including solubility, redox potential, number of electrons involving redox processes, diffusion coefficient, electron transfer rate constants, and membrane permeability? 2) How do the functional groups of redox active molecules influence their chemical and electrochemical stabilities in both charged and discharged states? and 3) Can superior redox active molecules be developed through in-depth mechanistic understandings to enable high energy and high power densities, long cycling redox flow batteries?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.