Electrochemical decomposition of choline chloride based ionic liquid analogues
Electrochemical decomposition of choline chloride based ionic liquid analogues
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DOI：
10.1039/b906318h
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发表时间：
2009-01-01
期刊：
影响因子：
9.8
通讯作者：
Van der Bruggen, Bart
中科院分区：
文献类型：
--
作者：
Haerens, Kurt;Matthijs, Edward;Van der Bruggen, Bart
离子液体在电化学应用中得到了广泛的研究，更具体地说是在金属的电沉积中。本文研究了氯化胆碱和乙二醇组成的低共熔溶剂在较长时间的电解过程中的电化学稳定性。观察到几种分解产物如2-甲基-1，3-二氧戊环的形成。给出了这些产物形成的可能机制：一些产物涉及在阳极或阴极的反应，而另一些则可以通过在两个电极处形成的反应产物的连续反应来解释。还可以检测到一系列氯化产品，如氯甲烷、二氯甲烷和氯仿。这是值得注意的，因为在阳极处没有观察到氯气的析出。氯化产物的形成归因于溶液中Cl-3（-）离子的存在。通过光度法观察到Cl-3（-）离子的存在。氯化产物的存在会对环境产生更大的影响，并对健康和安全带来更高的风险，并质疑这些离子液体类似物的“绿色”。为了减少溶剂的分解，加入水和易氧化的酸作为“牺牲剂”。定量了它们对2-甲基-1，3-二氧戊环形成的影响。然而，添加牺牲剂并没有改善溶剂的稳定性。甲酸的加入减少了2-甲基-1，3-二氧戊环的形成，但仍然可以检测到氯化产物。水减少了氯化产物的形成。
Ionic liquids are studied intensively for electrochemical applications and more specifically for the electrodeposition of metals. In this paper the electrochemical stability of a deep-eutectic solvent based on choline chloride and ethylene glycol is studied over longer periods of electrolysis. The formation of several decomposition products such as 2-methyl-1,3-dioxolane was observed. Possible mechanisms for the formation of these products are given: some products involve a reaction at either the anode or the cathode, while others can be explained by consecutive reactions of reaction products formed at both electrodes. A range of chlorinated products like chloromethane, dichloromethane and chloroform could be detected as well. This is remarkable as evolution of chlorine gas at the anode is not observed. The formation of the chlorinated products is ascribed to the existence of the Cl-3(-) ion in the solution. The presence of the Cl-3(-) ion was observed photometrically. The presence of chlorinated products gives rise to a larger environmental impact and higher risks for health and safety, and it questions the "greenness" of these ionic liquid analogues. To reduce the decomposition of the solvent, water and easily oxidizable acids were added as 'sacrificial agents'. Their influence on the formation of 2-methyl-1,3-dioxolane was quantified. However, the addition of the sacrificial agents did not improve the stability of the solvent. Addition of formic acid reduced the formation of 2-methyl-1,3-dioxolane but chlorinated products could still be detected. Water reduced the formation of chlorinated products.