Investigating Ionic Liquids in Electrochemical Applications

The Chemical and Biological Engineering department will be hosting a seminar featuring Assistant Professor of Chemical Engineering at City College of New York, Dr. Elizabeth J. Biddinger. The topic of the seminar will be Investigating Ionic Liquids in Electrochemical Applications.

Abstract

Ionic liquids (ILs) are salts with melting points below 100°C and can be tuned to the desired properties by modifying the anion-cation pair. Beyond the desirable traits many ILs are touted for in general applications, such as a minimal vapor pressures, high (and tunable) solubilities, etc., there are additional properties that make them desirable for electrochemical use. These include wide electrochemical potential windows (EWs) and moderate conductivities. Traditional electrochemical systems are commonly limited by either the EW or conductivity. In aqueous solutions the conductivities can be high by dissolving appreciable quantities of electrolyte, but the EW is small due to water splitting. This small EW prevents many electrochemical redox potentials from being accessed. In organic solutions, the EW can be increased but solubility of electrolyte salts is limited, reducing conductivity significantly. With the use of ILs, the EW can be substantially widened compared to aqueous systems while having higher conductivities than what is possible in many organic systems, potentially creating a more favorable electrochemical environment. Two applications where ILs hold promise for use will be presented – electrodeposition in ILs ultimately for recovery of fission products and use of IL-like materials as reversible electrolytes ultimately for applications in electo-organic syntheses and electrodeposition.

ILs have been investigated as extraction media for the separation of fission product slurries because of their tunable ligating effects. Once fission product cations are in the IL, they must be transformed into a stable waste form. Electrodeposition of the fission product cations creates a stable, solid waste form.

The electrochemistry and electrodeposition phenomena of palladium will be presented as a model fission product. Electrolytes in electrochemical solutions can be a contaminant to post-processing. By using a system that can be switched on and off as an electrolyte, salt contamination can be minimized. Silylamine reversible ionic liquids have been shown to have switchable properties between those of a molecular liquid (ML) organic solvent–like state and a reversible ionic liquid (RevIL) IL-like state. The switch to RevIL occurs with the introduction of carbon dioxide. The switch from RevIL back to ML occurs with moderate heating. The results of the investigation of triethoxysilylpropylamine as a model RevIL in electrochemical applications will be presented.