Ionization at a solid-water interface in an applied electric field: Charge regulation

Ryuichi Okamoto, Akira Onuki

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

We investigate ionization at a solid-water interface in an applied electric field. We attach an electrode to a dielectric film bearing silanol or carboxyl groups with an areal density Γ0, where the degree of dissociation α is determined by the proton density in water close to the film. We show how α depends on the density n0 of NaOH in water and the surface charge density σm on the electrode. For σm > 0, the protons are expelled away from the film, leading to an increase in α. In particular, in the range 0 < σm < eΓ0, self-regulation occurs to realize α ≅ σm/eΓ0 for n0 nc, where nc is 0.01 mol/L for silica surfaces and is 2 � 10-5 mol/L for carboxyl-bearing surfaces. We also examine the charge regulation with decreasing the cell thickness H below the Debye length κ-1, where a crossover occurs at the Gouy-Chapman length. In particular, when σm ∼ eΓ0 and H κ-1, the surface charges remain only partially screened by ions, leading to a nonvanishing electric field in the interior.

Original languageEnglish
Article number124706
JournalJournal of Chemical Physics
Volume145
Issue number12
DOIs
Publication statusPublished - Sep 28 2016
Externally publishedYes

Fingerprint

Bearings (structural)
Ionization
Electric fields
Surface charge
ionization
electric fields
Protons
Water
water
Electrodes
Dielectric films
Charge density
Silicon Dioxide
Debye length
electrodes
carboxyl group
Cells
Ions
crossovers
dissociation

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

Cite this

Ionization at a solid-water interface in an applied electric field : Charge regulation. / Okamoto, Ryuichi; Onuki, Akira.

In: Journal of Chemical Physics, Vol. 145, No. 12, 124706, 28.09.2016.

Research output: Contribution to journalArticle

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