Water and ions in electrified silica nano-pores: a molecular dynamics study

Tavakol, Mahdi; Voïtchovsky, Kislon

Abstract

Solid–liquid interfaces (SLIs) are ubiquitous in science and technology from the development of energy storage devices to the chemical reactions occurring in the biological milieu. In systems involving aqueous saline solutions as the liquid, both the water and the ions are routinely exposed to an electric field, whether the field is externally applied, or originating from the natural surface charges of the solid. In the current study a molecular dynamics (MD) framework is developed to study the effect of an applied voltage on the behaviour of ionic solutions located in a ∼7 nm pore between two uncharged hydrophilic silica slabs. We systematically investigate the dielectric properties of the solution and the organisation of the water and ions as a function of salt concentration. In pure water, the interplay between interfacial hydrogen bonds and the applied field can induce a significant reorganisation of the water orientation and densification at the interface. In saline solutions, at low concentrations and voltages the interface dominates the whole system due to the extended Debye length resulting in a dielectric constant lower than that for the bulk solution. An increase in salt concentration or voltage brings about more localized interfacial effects resulting in dielectric properties closer to that of the bulk solution. This suggests the possibility of tailoring the system to achieve the desired dielectric properties. For example, at a specific salt concentration, interfacial effects can locally increase the dielectric constant, something that could be exploited for energy storage.

Citation

Tavakol, M., & Voïtchovsky, K. (2024). Water and ions in electrified silica nano-pores: a molecular dynamics study. Physical Chemistry Chemical Physics, 26(33), 22062-22072. https://doi.org/10.1039/d4cp00750f

• Journal Article Type: Article
• Acceptance Date: Jul 26, 2024
• Online Publication Date: Jul 30, 2024
• Publication Date: Sep 7, 2024
• Deposit Date: Aug 22, 2024
• Publicly Available Date: Aug 22, 2024
• Journal: Physical Chemistry Chemical Physics
• Print ISSN: 1463-9076
• Electronic ISSN: 1463-9084
• Publisher: Royal Society of Chemistry
• Peer Reviewed: Peer Reviewed
• Volume: 26
• Issue: 33
• Pages: 22062-22072
• DOI: https://doi.org/10.1039/d4cp00750f
• Public URL: https://durham-repository.worktribe.com/output/2745963