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Ion correlations drive charge overscreening and heterogeneous nucleation at solid–aqueous electrolyte interfaces

Author(s): Lee, Sang Soo; Koishi, Ayumi; Bourg, Ian C; Fenter, Paul

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Abstract: Classical electrical double layer (EDL) models are foundational to the representation of atomistic structure and reactivity at charged interfaces. An important limitation to these models is their dependence on a mean-field approximation that is strictly valid for dilute aqueous solutions. Theoretical efforts to overcome this limitation are severely impeded by the lack of visualization of the structure over a wide range of ion concentration. Here, we report the salinity-dependent evolution of EDL structure at negatively charged mica–water interfaces, revealing transition from the Langmuir-type charge compensation in dilute salt solutions to nonclassical charge overscreening in highly concentrated solutions. The EDL structure in this overcharging regime is characterized by the development of both lateral positional correlation between adsorbed ions and vertical layering of alternating cations and anions reminiscent of the structures of strongly correlated ionic liquids. These EDL ions can spontaneously grow into nanocrystalline nuclei of ionic compounds at threshold ion concentrations that are significantly lower than the bulk solubility limit. These results shed light on the impact of ion cooperativity that drives heterogeneous nonclassical behaviors of the EDL in high salinity conditions.
Publication Date: 5-Aug-2021
Citation: Lee, Sang Soo, Koishi, Ayumi, Bourg, Ian C, Fenter, Paul. (2021). Ion correlations drive charge overscreening and heterogeneous nucleation at solid–aqueous electrolyte interfaces. Proceedings of the National Academy of Sciences, 118 (32), 10.1073/pnas.2105154118
DOI: doi:10.1073/pnas.2105154118
ISSN: 0027-8424
EISSN: 1091-6490
Language: en
Type of Material: Journal Article
Journal/Proceeding Title: Proceedings of the National Academy of Sciences
Version: Final published version. This is an open access article.

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