Ion Distributions at ElectrifiedWater-Organic Interfaces: PB-PMF Calculations and Impedance Spectroscopy Measurements

The interface between two immiscible electrolyte solutions consisting of alkali chlorides in water and the organic electrolyte BTPPATPFB in 1,2-dichloroethane is characterized with X-ray reflectivity, interfacial tension and impedance spectroscopy measurements over a range of applied voltage between the bulk solutions. X-ray reflectivity probes the interfacial ion distribution on the sub-nanometer length scale, whereas interfacial tension and impedance spectroscopy characterize quantities such as interfacial excess charge and differential capacitance that represent integrations over the interfacial ion distribution. Predictions of interfacial ion distributions by the recently introduced PB-PMF method, which combines Poisson's equation with ion potentials of mean force, provide excellent agreement, within one to two experimental standard deviations, with both X-ray reflectivity and interfacial tension measurements. However, the agreement with the differential capacitance measured by impedance spectroscopy, and modeled by the Randles equivalent circuit, is not as good. Values of measured and calculated differential capacitance can deviate by as much as 20% for applied electric potential differences larger than approximately ±100 mV. These comparisons indicate that our understanding of the ion distributions that underlie these measurements is adequate, but that further understanding of the modeling of impedance spectroscopy data is required for quantitative agreement at larger applied electric potential differences.
Rozhraní mezi dvě nemísitelnými roztoky elektrolytu, sestávající z alkalických chloridů ve vodě a organického elektrolytu BTPPATPFB v 1,2-dichlorethanu, je zkoumáno RTG odrazivostí, mezifázovým napětím a měřením impedanční spektroskopií.

Keywords

Impedance, modelling, ITIES, PB-PMF, Impedance, modelování, ITIES, PB-PMF

Citation

JOURNAL OF THE ELECTROCHEMICAL SOCIETY. 2015, vol. 162, issue 12, p. H890-H897.
https://iopscience.iop.org/article/10.1149/2.0621512jes

Document type

Peer-reviewed

Document version

Published version

Language of document

en

Document licence

Creative Commons Attribution 4.0 International
http://creativecommons.org/licenses/by/4.0/