Structure of the Electrical Double Layer Revisited: Electrode Capacitance in Aqueous Solutions
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Authors
Khademi, Mahmoud
Barz, Dominik P. J.
Date
2020-04-28
Type
journal article
Language
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Alternative Title
Abstract
The structure of the electrical double layer at the interface of planar electrodes and aqueous solutions is investigated. Electrical impedance spectroscopy is used to measure the impedance of aqueous solutions of sodium chloride and two different surfactants over a wide range of concentrations. The electrode capacitance is directly inferred from the admittance spectra as well as by regression of the impedance spectra to an equivalent circuit. It is found that the electrode capacitance remains on the same order of magnitude over the entire range of investigated concentrations. This is contradictive to the predictions of the Gouy–Chapman–Stern theory which predicts that, at low concentrations, the electrode capacitance should be determined by the diffuse layer. It is concluded that the Stern layer capacitance always dominates the electrode capacitance, even at very low concentrations, and the establishment of a diffuse layer capacitance requires an ionic strength of around 1 mM.
Description
Citation
Khademi, M., & Barz, D. P. J. (2020). Structure of the Electrical Double Layer Revisited: Electrode Capacitance in Aqueous Solutions. Langmuir, 36(16), 4250–4260. doi:10.1021/acs.langmuir.0c00024
Publisher
American Chemical Society (ACS)
License
Final publication available at: http://dx.doi.org/10.1021/acs.langmuir.0c00024