We investigated the thermophysical and electrochemical properties of eight model protic ionic liquids (PILs) primarily because of our interest in their proton conductivity and low volatility. The chemical structures of the cations (ammonium vs imidazolium) and anions (mesylate vs triflate) were found to strongly govern properties such as density, viscosity, ionic conductivity, thermal and electrochemical stability, and phase transition behaviors. Structure–property relations were analyzed on the basis of charge delocalization, cation π-stacking, van der Waals interactions of alkyl tails, and hydrogen bonding interactions between cations and anions. The diffusion coefficients of the free proton, the cation, and the anion were determined by using NMR spectroscopy, and were used to differentiate between the vehicular and Grotthuss mechanisms of diffusion of protons. A correlation, based on the Sutherland–Einstein equation, was developed to predict ionic conductivity by using the room temperature molar volume and the VFT equation for viscosity.

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The primary goal of this study was to explore the fundamental chemical processes occurring during a pulsed electrical discharge in liquid methanol. To this end, advanced analytical techniques were used to identify and, when possible, quantify gas and liquid methanol decomposition products. The effects of applied voltage, voltage polarity, and presence of water on the reaction stoichiometry and the selectivity for the identified gas products were also studied. Density Functional Theory (DFT) simulations were used to determine the most feasible thermal reaction pathways between 300 and 4000 K responsible for the formation of experimentally identified gas and liquid products. From these results, the key chemical reaction pathways were theorized and a reaction mechanism was developed. Gas products of plasmainduced decomposition of methanol that were detected and quantified include hydrogen, carbon monoxide, carbon dioxide, methane, acetylene, ethylene, and ethane. The reaction selectivity was the highest for the former two compounds regardless of the applied voltage, discharge polarity or presence of water in the starting solution. Results also showed that the applied voltage, discharge polarity and presence of water had no effect on the types of reaction products.Liquid methanol decomposition products that where identified include ethanol, ethylene glycol, formaldehyde, acetic acid, allyl alcohol, 1-propanol, 3-buten-1-ol, 3-butyn-1-ol, glycolaldehyde, and methyl glycolate. The chemical reaction mechanism that was proposed to explain the formation of the experimentally verified gas products offers specific pathways for the production of carbon monoxide and short-chained hydrocarbons. In contrast, the reactions leading to the formation of hydrogen, carbon dioxide, and liquid products appear to be random.

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