In this project funded by the Chemical Structure Dynamics and Mechanism (CSDM-A) program of the Chemistry Division, Professor Joshua Sangoro of The University of Tennessee, Knoxville is using advanced experimental techniques to study the structure of ionic liquids, which are liquids composed of positive and negative ions. Unlike ionic solids (such as table salt, Na+ Cl-), the fluid form of ionic liquids (also called molten salts) makes them potentially useful for a variety of technological applications, such as batteries, fuel cells and the solvents for the synthesis of other molecules. Just as liquid water actually contains areas that are ice-like in their ordering, ionic liquids can also possess local ordering of ionic molecules. The extent of ordering in ionic liquids influences their physical properties (e.g., density, viscosity, ability to conduct electricity). Professor Sangoro and his team seek to understand how ions organize in the liquid state, how long the arrangements persists, and how these arrangements are changed by interfaces such as the ionic liquid-air interface, or the interface between the liquid and a metal surface(where the metal may be a catalyst or an electrode for chemical reactions). The Sangoro group uses x-ray and neutron scattering techniques and a technique called broadband dielectric spectroscopy to obtain information about the structure and behavior of ionic liquids. This information may aid in the development of new clean energy and battery technologies. The main goal of the educational and outreach plans is to increase student interest in, exposure to, and preparation for careers in science and engineering, with specific focus on minority students. Professor Sangoro organizes mentored research experiences for high school students from underrepresented/minority and economically disadvantaged local groups, by first introducing engineering undergraduate students to research within the first two years of college. The research group partners with established NSF-funded outreach programs at the University of Tennessee to attract and retain engineering students from underrepresented groups, providing new research and training opportunities to graduate, undergraduate, and high school students in order to provide state-of-the-art research opportunities. Professor Sangoro engages in individualized mentoring for selected K-12 students from underrepresented groups in the economically disadvantaged groups living in the East Knoxville area. This CAREER grant enables the research team to provide hands-on training to both graduate and undergraduate students as well as high school students who may go on to become future scientists and engineers.
The project focuses on understanding the impact of mesoscale organization on interfacial ion dynamics in bulk and confined molecular ionic liquids. Upon systematic variation of the chemical composition of ionic liquids, the mesoscale organization and dynamics are probed by x-ray and neutron scattering, dynamic mechanical spectroscopy, and broadband dielectric spectroscopy. These complementary techniques enable the correlation of mesoscale structures, and an understanding of their dynamics and the resulting physical and chemical properties of ionic liquids. The second emphasis of this research project is on elucidating the correlation between of mesoscale organization and dynamics within the electrochemical double layers in molecular ionic liquids. This effort involves development of a new theoretical model to describe the processes associated with accumulation of ions at interfaces between ions and solid electron conductors. The third thrust of the project focuses on experiments to understand the impact of geometric confinement on mesoscale organization and dynamics. To achieve this, silica nanopores with mean diameters as small as 4 nanometers are prepared through electrochemical etching and filled with systematic series of ionic liquids. The interactions between ionic liquids and the pore walls are intentionally varied while measuring the dynamics associated with the ions. The series of experiments and computations leads to a molecular-level understanding of the influence of mesoscopic organization on interfacial ion dynamics and transport in bulk and confined molecular ionic liquids. The fundamental understanding gained from these studies enables rational development of more efficient systems of ionic liquids for different applications including uses in electrochemical power sources and devices. The broader impacts of this work include potential societal benefits from an increased understanding of ionic liquids, as well as training of students and postdoctoral associates in fundamental science underlying many electrochemical energy technologies.
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.
