As part of a center devoted to discovering new types of electrolytes for energy storage, our research explores microemulsions as breakthrough electrolytes for integration into redox flow batteries (RFBs). Microemulsions are thermodynamically stable homogeneous solutions stabilized by surfactants in which oil and water do not separate. This unique solution enables us to decouple the electrical conductivity of aqueous salt solutions from the energy density of
the dissolved redox active molecule in the oil phase. The project provides perhaps the most comprehensive research on microemulsions reported.
Our investigations attempt to unravel the intricate behavior of physical properties and the structure of microemulsions when interfaced with electrified environments. After determining phase diagrams of the mixtures to identify regions in which the microemulsions were likely to be homogeneous and bicontinuous, we have carried out extensive characterization of their structure using multiple methods including neutron scattering and NMR methods. We examine the structural dynamics governing microemulsions in the bulk and at the electrode interfaces using techniques such as neutron reflectivity and computational probes. This comprehensive understanding is instrumental in deciphering the mechanisms underlying electron transfer reactions within these systems, shedding light on their electrochemical performance and potential applications in energy storage technologies.
We then describe studies of electrochemistry of oil-soluble redox active species in microemulsions and their use in redox flow batteries (RFBs). We combine oil subphases containing hydrophobic redox active components with an aqueous subphase containing ions, thereby achieving aqueous-level conductivity with the broader selection and higher redox potential of organic redox material, creating a unique electrolyte type for the RFB. Initially, we studied the electrochemistry of ferrocene in bi-continuous TWEEN/toluene/water microemulsions, with ferrocene dissolved in the toluene. Remarkably facile electrochemistry was observed, leading to a hypothesis concerning the ionic transfer processes associated with the formation of ferricenium ion. A principal question was whether the ferricenium is ejected from the liquid phase, a process that seems incompatible with the facile electrochemistry. We will elaborate on the possible process occurring. To further elucidate this process, a series of ring-substituted ferrocene derivatives of varying hydrophobic character was studied, as was the effects of including hydrophobic salts in the microemulsion.
To further inform aspects of the formulation of microemulsions for flow batteries, we augmented our experimental work with several machine-learning studies to discover microemulsion and electroactive component information.
Finally, RFBs based on these systems will be described, including some discussion of the interactions of the microemulsions with porous electrodes and membrane separators. In addition to that discussion, we will describe recent work with possible alternative electrolytes for use in the microemulsion-RFB.
27/04/2026
Microemulsions as Electrolytes: Physical Properties, Structure and Electrochemistry
di Thomas A. Zawodzinski, University of Tennessee-Knoxville, USA
Il seminario si terrà lunedì 27 aprile p.v. alle ore 12.15 in Sala Parravano, ed. Cannizzaro (CU014)
THOMAS A. ZAWODZINSKI, JR., PH.D.
Thomas Zawodzinski is presently the Governor’s Chair in Electrical Energy Conversion and Storage, with appointments in the Chemical and Biomolecular Engineering Dept. at the University of Tennessee-Knoxville and at ORNL. He previously was the Ohio Eminent Scholar in Fuel Cells at Case Western Reserve University, Director of the Case
Advanced Power Institute, and the founding Director of the Wright Fuel Cell Group. Dr. Zawodzinski is a Fellow of the Electrochemical Society and of the American Chemical Society Polymer Division. Throughout his career, Dr. Zawodzinski has played leadership roles in projects on fuel cell materials and systems, especially in the development of new
polymeric membranes for automotive applications at elevated temperature and low relative humidity. He has made significant contributions in electro-catalysis, gas diffusion media and fuel cell durability, as well as in projects related to redox flow and metal-air batteries, electrochemical sensors, electro-responsive polymers, electro-separations and other applications of electrochemical technologies. He has published more than two hundred refereed papers, several book chapters and holds five patents.