Interfacial Fields Measured by Vibrational Sum Frequency Generation at Electrode-Electrolyte and Electrode-Ionic Liquid Interfaces
Abstract
The goal of this project was to understand the details of interfacial electric fields at the metal electrolyte junctions, with particular emphasis on ionic liquids (I Ls). The main experimental approach was to use vibrational Stark shift molecules tethered on the metal as probes of the interface. The most common probe used in our studies was benzonitrile, whose nitrile stretch served as the Stark probe. We achieved four goals using this approach. First, in our study of ILmetal junction we found out that the measured electric fields depended on the size of anions within a family of I Ls. Further computational work revealed that this arises due to a balance between packing density and surface electrostatics. Second, we found that ILs outcompete water by a large margin for adhesionto a metal. We noted that in mixtures of IL and water, the mole-fraction of bulk water had to exceed very large values (>0.95) for the water to overwhelm and dissolve the interfacial structure. Third, we studied the electric field at the junction of metals and surfactants, which are closely related to I Ls. We found out that the salvation structure of the surf act ant head is crucial in determining the magnitude of the interfacial field. Finally, in a more fundamental work, we established a connection between the organic chemistry concept of Hammett parameter and interfacial polarization using benzonitrile Stark shift probes. All of these projects have given us a more molecular understanding of the ionic structure and interfacial fields at metal-IL junctions, and can help in designing tailored I Ls for electrochemical applications.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 04, 2021
- Accession Number
- AD1146114
Entities
People
- Jahan M Dawlaty
Organizations
- University of Southern California