CAREER: Electrokinetic Flows and Electrochemical Dynamics in Concentrated Electrolytes and Ionic Liquids

Carnegie Mellon University, Pittsburgh PA

Investigators

Abstract

CAREER: Electrokinetic Flows and Electrochemical Dynamics in Concentrated Electrolytes and Ionic Liquids PI: Khair, Aditya Institution: Carnegie Mellon University Many liquid and particle systems in technology and biology contain ions, and in some of these systems, the concentration of ions is large. The theory that scientists and engineers use to predict the dynamics of these systems is based on assumptions that the ions can be considered to be point charges and that interactions among the ions are not important. The equations based on this theory work well for dilute ion concentrations, but they fail to predict interesting phenomena observed when the concentration of ions is large. Systems containing high concentrations of ions appear in many problems of technological and biological importance, including water desalination, the development of batteries and super-capacitors, and transfer of ions across cell membranes through ion channels. The goal of this project is to develop an integrated research and teaching program to develop a new model that scientists and engineers can use to describe the essential features of electrically driven transport in concentrated systems. Understanding such phenomena and training students to appreciate them will enhance manufacturing capabilities and may lead to new technological developments such as novel separation protocols for nanoparticles and biomolecules based on the motion of charged objects. The multi-tiered educational plan for the project includes outreach activities, undergraduate and graduate course design and research, technical software development, and organization of scientific meetings. This project will develop a continuum framework for electrically driven (electrokinetic) fluid flow and particle transport in concentrated electrolytes and ionic liquids, via a combination of modeling, computation, and experiment. Concentrated electrolytes and ionic liquids are attractive materials for energy storage and conversion technologies, but existing theoretical models fail to describe their dynamical response to applied voltages. The central hypothesis of the project is that explicit ion-ion interactions in concentrated systems, due to steric repulsion and electrostatic correlations, result in their dynamics being radically different from dilute solutions. Molecular simulations can quantify ion-ion interactions in equilibrium systems; however, they are often too computationally expensive to capture electrokinetic phenomena. Thus, there is a pressing need for a continuum-level theory that encapsulates the essential features of nonequilibrium transport in concentrated charge-carrying liquids in complex geometries. A model will be developed for anomalous electrokinetic transport in concentrated systems, including electrophoretic mobility reversals. The electrostatic forces between particles in concentrated electrolytes and ionic liquids will be quantified to predict suspension stability and flocculation in these media. The electrochemical dynamics of ionic liquids will be analyzed.