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Nonaqueous electrochemical thermodynamics
Abstract
Since the pioneering work by Debye and Hückel in the 1920s, the development of electrolyte theory and the understanding of the thermodynamic behavior of electrolyte solutions have taken many different paths. While the behaviors of many electrolytes in water are well described, the behavior of electrolytes in most solvents is incomplete. In addition, thermodynamic comparisons between salts in water and other solvents require information generally not available. This thesis extends the understanding of electrolyte behavior in two very important electrochemical solvents, acetonitrile and tetrahydrofuran. Three supporting electrolytes that are particularly important to the field of electrochemistry were studied using two experimental techniques. The three electrolytes were tetrabutylammonium hexafluorophosphate, potassium tetrakis(pentafluorophenyl)borate, and tetrabutylammonium tetrakis(pentafluorophenyl)borate. The first experimental technique used to study these electrolyte solutions was vapor pressure measurements. Precise vapor pressure measurements are a useful tool for calculated thermodynamic properties such as the activity coefficients. The osmotic coefficients were fit using the Pitzer equation and the resulting fitting parameters were used to calculate the activity coefficients. The second technique used was conductivity measurements. Conductivity measurements are a classical method to determine the behavior of electrolyte solutions. Properties of the electrolyte and solvent that affect the movement of the ions, and their interactions reveal themselves in the conductivity. Lastly, the equilibrium constants for the formation of ion pairs, also called association constants, were calculated using both the activity coefficients and the conductivity measurements. Both methods showed that association constants in acetonitrile were much smaller than in tetrahydrofuran. In addition, the tetrakis(pentafluorophenyl)borate anion electrolytes had smaller association constants than the hexafluorophosphate salt in the low dielectric constant solvent, tetrahydrofuran.
Subject Area
Analytical chemistry|Chemistry
Recommended Citation
Stafford, Nathan, "Nonaqueous electrochemical thermodynamics" (2006). ETD collection for University of Nebraska-Lincoln. AAI3230060.
https://digitalcommons.unl.edu/dissertations/AAI3230060