Professor Zahra Fakhraai (University of Pennsylvania) Seminar

Title: Evolution of Electrode Interfaces During Electrochemistry Abstract: Photoelectrochemical reactions have emerged as a direct pathway to harvest solar energy for sustainable chemistry. Understanding and controlling the complex microenvironments of charged electrodes or hybrid inorganic/organic interfaces is critical for optimizing a desired reaction and ensuring electrode/material durability. We utilize in situ electrochemical spectroscopic ellipsometry to measure the complex dielectric constant and index of refraction of the electrolyte interface. Using this approach, we monitor the evolution of the microenvironments of hybrid interfaces and independently measure the properties of the electric double layer, polymer stability, oxide formation and reduction, to disentangle the role of various factors in reaction evolution and electrode degradation. In aqueous electrolytes, we demonstrate that the orientation and restructuring of water can play a strong role in slowing the interfacial kinetics upon discharge, and show that this is primarily due to the formation of a metastable state where reorganization entropy compensates the change in the doubly layer enthalpy. In non-aqueous electrolytes, we demonstrate the strong interplay between additives and electrolyte oxidation states in reaction selectivity, by independently measuring the oxidation state change and the electrolyte kinetics in the absence or presence of surfactants. Overall, we show that by monitoring the interfacial dielectric constant in a probe-free manner, we can unravel the complexity of the microenvironments. Bio: Zahra Fakhraai is a Professor of Chemistry at the University of Pennsylvania, with a secondary appointment at the Department of Chemical and Biomolecular Engineering. She received her PhD degree in Physics from the University of Waterloo in 2007, where she studied the dynamics of polymers in thin films and at interfaces. After two postdoctoral fellowships at the University of Toronto (