Protic ionic liquids (PILs) are a vast class of compounds that are expected to play an increasing role as fuel cell electrolytes. A crucial aspect of these systems is represented by the reversible proton transfer reaction between a Bronsted acid and a Bronsted base giving rise to the ionic phase out of a molecular neutral state. Thermodynamic, structural and chemical properties of a prototypical PIL, ethylammonium nitrate (EAN), have been investigated by a combination of different computational approaches, ranging from ab initio to classical simulations based on a reactive Monte Carlo algorithm. Ab initio methods have been applied to map the potential energy surface and reaction energies of EAN-related molecules and small clusters. Crystal structures and vibrational properties of small clusters have also been investigated at the ab initio level. The ab initio data have been used to parametrise a reactive force field, able to reproduce the acid-base equilibrium of EAN, and which has subsequently been used to carry out a detailed investigation of the hydrogen bond network in liquid EAN, using the size of the hydrogen atom as a free parameter to explore a wide variety of conditions ranging from weak to strong hydrogen bonding. Equilibrium properties such as the crystal and liquid density are well reproduced by the model which provides only a rather crude description of fluidity and cohesive energy. In addition, Monte Carlo simulations have been carried out to investigate the properties of small EAN clusters in equilibrium with their vapour. The results show a complex pattern I of ionic and neutral molecular phases as a function of cluster size and thermodynamic conditions. As a side investigation, a simulation study of electrowetting and liquid-vapour nucleation for the restricted primitive model was carried out in order to clarify crucial aspects of Coulomb systems.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:557414 |
| Date | January 2012 |
| Creators | Martinez, N. C. Forero |
| Publisher | Queen's University Belfast |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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