Electrokinetics of the amphifunctional metal/electrolyte solution interface in the presence of a redox couple

J.F.L. Duval

Research output: Contribution to journalArticleAcademicpeer-review

24 Citations (Scopus)

Abstract

Double layers (DL) at amphifunctionally electrified interfaces, such as that of an oxidized metal in an aqueous electrolyte solution, arise from coupling between ionic and electronic surface-charging processes. The electronic component enters the double-layer formation in the well-known situation where a potential is externally applied. In that case, the DL is fully or partly polarized depending on the possibility of interfacial electron transfer, that is, a faradaic process. This paper reports on the conjunction of the chemical/electrochemical processes at the interface in the case where the solution contains a redox-active couple. This makes it possible to polarize/depolarize a DL without invoking any external circuit. Streaming potential data obtained for the gold/(Fe(CN)63-/Fe(CN)64-, KNO3) electrolyte interface are analyzed in terms of a recently developed theory which takes into account reversible bipolar faradaic depolarization, the inherent nonlinearity of the lateral field, and the effects of flow on the rate of the faradaic reactions. It appears that the theory largely overestimates the bipolar currents, leading to physically unrealistic ¿-potentials. A careful analysis of monopolar voltammetric data reveals quasi-reversible behavior of the redox couple under the typical convective conditions and electrolyte compositions met in electrokinetic experiments. Inclusion of reduced reversibility (the extent of which is position-dependent under the streaming-potential measurement conditions) leads to a consistent set of ¿-potentials which compare well to the values for the background electrolyte.
Original languageEnglish
Pages (from-to)211-223
JournalJournal of Colloid and Interface Science
Volume269
Issue number1
DOIs
Publication statusPublished - 2004

Keywords

  • double-layer forces
  • high surface-potentials
  • lateral electric-field
  • faradaic depolarization
  • microscope
  • voltammetry
  • gold

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