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Preparation of Binary and Ternary Deep Eutectic Systems
Published on: October 31, 2019
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Electron Transfer Kinetics in a Deep Eutectic Solvent.
Fangchen Zhen1, Lucie Percevault1, Ludovic Paquin1
1Univ Rennes , CNRS, ISCR - UMR 6226 , F-35000 Rennes , France.
The Journal of Physical Chemistry. B
|January 24, 2020
Summary
Electron transfer (ET) kinetics in Ethaline, a deep eutectic solvent, are nearly as fast as in traditional solvents, unlike in ionic liquids. This study measured ET rate constants for key redox couples, finding minimal slowdown in Ethaline.
Area of Science:
- Electrochemistry
- Physical Chemistry
- Materials Science
Background:
- Electron transfer (ET) is fundamental to many chemical and biological processes.
- Understanding ET kinetics in novel solvent systems is crucial for developing new electrochemical applications.
- Deep eutectic solvents (DES) offer unique properties but their impact on ET kinetics remains less explored compared to ionic liquids and conventional solvents.
Purpose of the Study:
- To measure and compare electron transfer (ET) kinetic rate constants (ks) in Ethaline (a specific DES) with those in conventional solvents and ionic liquids.
- To investigate the influence of solvent properties, specifically solvent relaxation time, on ET kinetics.
- To evaluate the suitability of Ethaline as a medium for electrochemical reactions.
Main Methods:
- Electrochemical measurements using a glassy carbon electrode.
- Quantification of electron transfer rate constants for ferrocene/ferrocenium and ferrocyanide/ferricyanide redox couples.
- Correction for ohmic drop in the deep eutectic solvent (DES) measurements.
- Analysis of data using Marcus Theory, considering solvent relaxation time.
Main Results:
- Electron transfer rate constants in Ethaline were found to be only slightly lower (≤50%) than those in classical solvents like acetonitrile and water.
- In contrast, ET rates in ionic liquids were significantly slower, being up to 100 times lower than in Ethaline.
- The observed kinetics align with predictions based on Marcus Theory for adiabatic electron transfer.
Conclusions:
- Ethaline exhibits favorable electron transfer kinetics, performing comparably to conventional solvents and significantly better than ionic liquids.
- The findings suggest that DES, like Ethaline, can be effective media for electrochemical processes where fast electron transfer is required.
- Solvent relaxation time plays a key role in modulating electron transfer rates, as evidenced by the comparison across different solvent types.
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