Electrokinetic Streaming-Current Methods to Probe the Electrode-Electrolyte Interface under Applied Potentials

Prantik Saha, Changwoo Nam, Michael A. Hickner, Iryna V. Zenyuk

Research output: Contribution to journalArticle

1 Scopus citations

Abstract

At an electrified interface of metal and electrolyte, ion concentration in the diffuse layer is different from the bulk and is impacted by metal charge. The double-layer structure can significantly enhance local ionic conductivity. Understanding the conductivity enhancement with conventional electrochemical measurements is challenging; however, electrokinetic experiments can be more useful in probing local ionic conductivities. We used streaming-current experiments for a range of pH values to measure ζ-potential at metal-electrolyte interfaces. We extend the method by incorporating a three-electrode electrochemical cell where the potential of the metal can be varied. By using a range of applied potentials between -200 and 800 mV (vs standard hydrogen electrode), we explored how surface charging of Au electrode affects ζ-potential. An inflection point is observed on the plot of ζ-potential against applied potential, and this point is believed to be a potential of zero charge of the electrode. Using the Gouy-Chapman-Stern-Grahame model, we correlate measured ζ-potential values to metal surface charge and calculate ionic distribution and conductivity within the microchannel. Finally, ionic conductivity is calculated as a function of metal surface charge, and as expected, Gouy-Chapman theory shows a parabolic relationship.

Original languageEnglish (US)
Pages (from-to)19493-19505
Number of pages13
JournalJournal of Physical Chemistry C
Volume123
Issue number32
DOIs
StatePublished - Aug 15 2019

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

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