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

Sang Soo Lee, Ayumi Koishi, Ian C. Bourg, Paul Fenter

Research output: Contribution to journalArticlepeer-review

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 highsalinity conditions.

Original languageEnglish (US)
Article numbere2105154118
JournalProceedings of the National Academy of Sciences of the United States of America
Volume118
Issue number32
DOIs
StatePublished - Aug 10 2021

All Science Journal Classification (ASJC) codes

  • General

Keywords

  • Adsorption
  • EDL
  • Molecular dynamics
  • Salinity
  • X-ray reflectivity

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