The contrasting effects of diethylmethylamine during reduction of protons and oxidation of formic acid in diethylmethylammonium-based protic ionic liquids
The contrasting effects of diethylmethylamine during reduction of protons and oxidation of formic acid in diethylmethylammonium-based protic ionic liquids
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DOI：
10.1016/j.jelechem.2017.10.021
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发表时间：
2018-06-15
影响因子：
4.5
通讯作者：
Walsh, Darren A.
中科院分区：
文献类型：
--
作者：
Goodwin, Sean E.;Muhammad, Sayyar;Walsh, Darren A.
离子液体被正式定义为完全由离子组成的液体，并且是低于100摄氏度的液体。随着这些液体被提议用于一系列电化学装置和应用，了解它们的电化学行为变得越来越重要。在这篇文章中，我们描述了母体胺分子对质子离子液体二乙基甲基三氟甲烷磺酸铵和七氟丁酸二乙基甲基铵的电催化作用。我们首先证明了在三氟甲烷磺酸二乙基甲基铵中电催化还原三氟甲烷磺酸的过程中，二乙基甲胺可以吸附在Pt电极上。相反，二乙基甲胺通过将酸去质子化成活性甲酸，促进了离子液体中甲酸的氧化。因此，中性碱可以抑制或增强液体中的电催化作用，这取决于所考虑的反应。我们还表明，甲酸在七氟丁酸二乙基甲基铵中的氧化机制与在三氟甲烷磺酸二乙基甲基铵中观察到的氧化机制有很大不同。这一现象归因于中毒观众物质在电极表面的吸附，表明离子-液体阴离子结构的变化会对这些液体的电化学产生巨大影响。
Ionic liquids are formally defined as liquids that consist entirely of ions, and which are liquid below 100 degrees C. As these liquids are being proposed for use in a range of electrochemical devices and applications, understanding the electrochemical behaviour of these is increasingly important. In this contribution, we describe the effects of parent amine molecules on electrocatalysis in the protic ionic liquids diethylmethylammonium trifluoromethanesulfonate and diethylmethylammonium heptafluorobutanoate. We first show that diethylmethylamine can adsorb onto Pt electrodes during electrocatalytic reduction of trifluoromethanesulfonic acid in diethylmethylammonium trifluoromethanesulfonate. In contrast, diethylmethylamine promotes the oxidation of formic acid in this ionic liquid, by deprotonating the acid to the active formate species. Therefore, the neutral base can either inhibit or enhance electrocatalysis in the liquid, depending on the reaction under consideration. We also show that the mechanism of formic-acid oxidation in diethylmethylammonium heptafluorobutanoate differs significantly from that observed when using diethylmethylammonium trifluoromethanesulfonate. This phenomenon is attributed to adsorption of poisoning spectator species onto the electrode surface, demonstrating that changes to the structure of ionic-liquid anions can have drastic effects on the electrochemistry of these liquids.