Ionic Layering and Overcharging in Electrical Double Layers in a Poisson-Boltzmann Model

Ankur Gupta, Ananth Govind Rajan, Emily A. Carter, and Howard A. Stone
Phys. Rev. Lett. 125, 188004 – Published 30 October 2020
PDFHTMLExport Citation

Abstract

Electrical double layers (EDLs) play a significant role in a broad range of physical phenomena related to colloidal stability, diffuse-charge dynamics, electrokinetics, and energy storage applications. Recently, it has been suggested that for large ion sizes or multivalent electrolytes, ions can arrange in a layered structure inside the EDLs. However, the widely used Poisson–Boltzmann models for EDLs are unable to capture the details of ion concentration oscillations and the effect of electrolyte valence on such oscillations. Here, by treating a pair of ions as hard spheres below the distance of closest approach and as point charges otherwise, we are able to predict ionic layering without any additional parameters or boundary conditions while still being compatible with the Poisson–Boltzmann framework. Depending on the combination of ion valence, size, and concentration, our model reveals a structured EDL with spatially oscillating ion concentrations. We report the dependence of critical ion concentration, i.e., the ion concentration above which the oscillations are observed, on the counter-ion valence and the ion size. More importantly, our model displays quantitative agreement with the results of computationally intensive models of the EDL. Finally, we analyze the nonequilibrium problem of EDL charging and demonstrate that ionic layering increases the total charge storage capacity and the charging timescale.

  • Figure
  • Figure
  • Figure
  • Figure
  • Received 2 June 2020
  • Revised 6 September 2020
  • Accepted 30 September 2020

DOI:https://doi.org/10.1103/PhysRevLett.125.188004

© 2020 American Physical Society

Physics Subject Headings (PhySH)

Polymers & Soft MatterParticles & FieldsCondensed Matter, Materials & Applied PhysicsNonlinear Dynamics

Authors & Affiliations

Ankur Gupta1,2,*, Ananth Govind Rajan1,3, Emily A. Carter1,4,5, and Howard A. Stone1,†

  • 1Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544, USA
  • 2Department of Chemical and Biological Engineering, University of Colorado, Boulder, Colorado 80309, USA
  • 3Department of Chemical Engineering, Indian Institute of Science, Bengaluru, Karnataka 560012, India
  • 4Department of Chemical and Biomolecular Engineering, University of California, Los Angeles, Los Angeles, California 90095, USA
  • 5Office of the Chancellor, University of California, Los Angeles, Los Angeles, California 90095, USA

  • *ankur.gupta@colorado.edu
  • hastone@princeton.edu

Article Text (Subscription Required)

Click to Expand

Supplemental Material (Subscription Required)

Click to Expand

References (Subscription Required)

Click to Expand
Issue

Vol. 125, Iss. 18 — 30 October 2020

Reuse & Permissions
Access Options
Author publication services for translation and copyediting assistance advertisement

Authorization Required


×
×

Images

×

Sign up to receive regular email alerts from Physical Review Letters

Log In

Cancel
×

Search


Article Lookup

Paste a citation or DOI

Enter a citation
×