The effects of ion adsorption on the potential of zero charge and the differential capacitance of charged aqueous interfaces

Yuki Uematsu, Roland R. Netz, Douwe Jan Bonthuis

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

Using a box profile approximation for the non-electrostatic surface adsorption potentials of anions and cations, we calculate the differential capacitance of aqueous electrolyte interfaces from a numerical solution of the Poisson-Boltzmann equation, including steric interactions between the ions and an inhomogeneous dielectric profile. Preferential adsorption of the positive (negative) ion shifts the minimum of the differential capacitance to positive (negative) surface potential values. The trends are similar for the potential of zero charge; however, the potential of zero charge does not correspond to the minimum of the differential capacitance in the case of asymmetric ion adsorption, contrary to the assumption commonly used to determine the potential of zero charge. Our model can be used to obtain more accurate estimates of ion adsorption properties from differential capacitance or electrocapillary measurements. Asymmetric ion adsorption also affects the relative heights of the characteristic maxima in the differential capacitance curves as a function of the surface potential, but even for strong adsorption potentials the effect is small, making it difficult to reliably determine the adsorption properties from the peak heights.

Original languageEnglish
Article number064002
JournalJournal of Physics Condensed Matter
Volume30
Issue number6
DOIs
Publication statusPublished - Jan 17 2018

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Condensed Matter Physics

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