Molecular Interrogation of Coupled Electron- and Phase-Transfer Reactions

With support from the Chemical Structure, Dynamics, and Mechanisms A (CSDM-A) Program in the Division of Chemistry, Rodrigo Noriega of the University of Utah along with Henry White from the University of Utah and Gregory Voth from the University of Chicago will study coupled electron and phase transfer processes. These reactions, where electron transfer occurs alongside the transport of ions or neutral molecules across a phase boundary, are present in a wide variety of industrial processes and energy storage technologies. Understanding these reactions is challenging due to the lack of molecular-scale understanding of intermediates at critical steps in these multistep processes. Dr. Noriega and his team will integrate ultrafast spectroscopy and electrochemistry experiments on well-defined molecular systems with computational methods to study coupled electron and phase transfer reactions independently. The resulting insight into these reactions has the potential to impact energy storage and rare metal ion separations. In addition to training students in research, the team will organize an annual workshop that includes lab demonstrations and professional development opportunities. Probe reactions at complex interfaces, whereby redox-active analytes undergo electron transfer with an electrode while also transferring between two immiscible phases due to the differential solubility of their oxidation states, will be studied with voltammetry at three-phase interfaces, as well as by ultrafast transient absorption spectroscopy, and multiscale electrochemical molecular dynamics simulations. To inform and test new models that capture molecular-scale dynamics and macroscopic outcomes, a hierarchical framework that combines computation with spectroscopic and electrochemical observation spanning orders of magnitude in time and length will be employed. The energetics and dynamics of solvation shell exchange, including the role of fluctuations at the interface, will be determined by correlating phase-specific electrochemical responses, time-resolved absorption and emission measurements at phase boundaries under controlled electrostatic conditions, and multiscale molecular dynamics simulations. Independently monitoring the ion- and electron-transfer currents at well-defined interfaces while systematically altering their electric double layer structure, along with efficient constant-potential electrochemical simulation, will identify the role of molecular structure of relevant coupled electron and phase transfer reactions at three-phase interfaces. 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.