Analysis of Facilitated Ion Transfer across Liquid-Liquid Interfaces Using Collision Electrochemisty

doi:10.1016/S1872-2040(20)60060-3

Chinese Journal of Analytical Chemistry

Volume 48, Issue 11, November 2020, Pages 1535-1541

https://doi.org/10.1016/S1872-2040(20)60060-3 Get rights and content

Abstract

An electrochemical method was developed to analyze the alkali metal ion transfer across the water/1,2-dichloroethane interfaces facilitated by dibenzo-18-crown-6 ether (DB18C6) by observing the collisions of single emulsion droplets on an ultramicroelectrode (UME). The water-in-oil emulsion droplets were stabilized by an ionic liquid of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imides, in which a highly hydrophilic redox probe of potassium ferrocyanide/ferricyanide (K₃Fe(CN)₆/ K₄Fe(CN)₆) was used. When the droplets collided with the UME that was biased at a potential to drive the oxidation reaction of [Fe(CN)₆]⁴⁻ (0.05 mol/L), the current spikes could be observed only with the addition of DB18C6. It was suggested that the DB18C6 as K⁺ ionophore facilitated the K⁺ transfer from the water to the oil to maintain charge balance during the electrolysis. As more K⁺ ionophores were added, the integrated charge of the current spikes showed a rising trend in general because of the ionophore to lower the Gibbs energy of ion transfer. Further collision experiments were conducted to investigate the transfer of Na⁺ and K⁺ cations facilitated by the DB18C6. The order in which the “voltammetric” oxidation waves appeared indicated that the ionophore of DB18C6 was more efficient in carrying K⁺ across the water/1,2-Dichloroethane interface. Thereby, the collision electrochemistry is a convenient and effective mean to study the ion selectivity of ionophore.

Graphical abstract

In collision-based electrochemical measurements, the presence of the DB18C6 ionophore facilitated the transfer of alkali metal ions from the water to the oil to maintain charge balance during electrolysis in the droplets, and thus the facilitated ion transfer reactions by the DB18C6 as the rate-determining step were characterized by the collision currents. The order in the ‘voltammetric’ waves built by plotting the average magnitude of normalized collision charges vs. the applied potentials indicated that the DB18C6 was more efficient in carrying K⁺ across the water/1,2-Dichloroethane interface, compared to Na⁺.

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: This work was supported by the National Natural Science Foundation of China (Nos. 21705128, 21675124) and the Natural Science Basic Research Plan in Shaanxi Province of China (No. 2018JQ2006).

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RESEARCH PAPERAnalysis of Facilitated Ion Transfer across Liquid-Liquid Interfaces Using Collision Electrochemisty

Abstract

Graphical abstract

Electrochim. Acta

J. Electroanal. Chem. Interfacial Electrochem.

J. Electroanal. Chem.

Electrochim. Acta

Chem. Sci.

Bull. Chem. Soc. Jpn.

J. Phys. Chem. B

ChemElectroChem

J. Am. Chem. Soc.

Anal. Chem.

Proc. Natl. Acad. Sci. USA

Angew. Chem. Int. Ed.

RESEARCH PAPER
Analysis of Facilitated Ion Transfer across Liquid-Liquid Interfaces Using Collision Electrochemisty