(605h) Anion Effects on the Interfacial Structure and Bulk Physical Properties in Deep Eutectic Solvents

Deep eutectic solvents (DESs) have tunable physical properties and are promising electrolytes for energy storage due to their wide electrochemical windows, high solvent strength, and extremely low volatility. While bulk properties of DESs have been more thoroughly studied, interfacial properties are still not well understood in these systems. In this work, electrochemical impedance spectroscopy (EIS) and surface-enhanced Raman spectroscopy (SERS) were used to investigate the interfacial structure formed in choline-based DESs with varied hydrogen bond acceptor anions. Anion variation alters the strength of the bonding environments in DESs, impacting both interfacial structures, as well as the bulk properties of the fluid such as surface tension, density, viscosity, and conductivity. EIS and SERS combined, give a more complete picture of the interfacial structure in these multicomponent systems. Glassy carbon (GC), gold (Au), and platinum (Pt) surfaces were used to compare general charge distribution, surface adsorption, and solvation of DESs components at both metal and non-metal interfaces. This work contributes to the fundamental understanding of the interfacial behavior, and physical properties of DESs with varied anions. Fundamental studies of the properties of DESs are vital if DESs are to be realized in energy storage applications.