Doctoral Thesis
Ion Specific Effects in Equilibrium Modelling of Electrolytes
Doctor of Philosophy (PhD), Murdoch University
Abstract
When a charged surface comes in contact with an electrolyte solution, an ion adsorption layer, often referred to as an electric double layer (EDL), is formed. This structure plays a crucial role in phenomena ranging from protein adsorption in cells and related small biological systems, to mid-scale electrowetting applications, to large industrial energy storage applications, specifically supercapacitors or electric double-layer capacitors (EDLC). Correctly modeling the structure and the underlying interaction mechanism will help optimize the efficiencies of these devices. In mean-field theories, these EDL structures have been modeled based on the assumption that the electrolyte ions are point particles in a continuous dielectric solvent medium interacting only electrostatically. While these assumptions are simple and efficient in dilute and low-potential solutions, the model fails in concentrated (> 0.1M) and high-potential solutions (> 100mV) applications. In this thesis, we address the impact that steric models, introducing finite ion size effects, have on the structure and performance, such as the differential capacitance and the total free energy of an EDL. We derive analytical and semi-analytical approximations for these numerically rather expensive steric models. We show that at high electrolyte concentration and potential, these approximations converge to that of the full numerical solutions. We apply the different steric models in an electrowetting application to examine the role of finite size effects on the contact angle of electrolyte solutions on electrode surfaces. Finally, we also introduce microscopic non-electrostatic interactions such as a cavity, interface, and dispersion interactions in the model to study the effects that ion-specific polarisabilities and cavity formation play in determining the structure of ion adsorption layers and the performances of EDLC devices.
Details
- Title
- Ion Specific Effects in Equilibrium Modelling of Electrolytes
- Authors/Creators
- Dagmawi B Tadesse
- Contributors
- Drew Parsons (Supervisor)Bruce Gardiner (Supervisor) - Murdoch University, Centre for Molecular Medicine and Innovative TherapeuticsPiotr Kowalczyk (Supervisor) - Murdoch University, Centre for Water, Energy and Waste
- Awarding Institution
- Murdoch University; Doctor of Philosophy (PhD)
- Identifiers
- 991005583969507891
- Murdoch Affiliation
- School of Mathematics, Statistics, Chemistry and Physics
- Resource Type
- Doctoral Thesis
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