Electroanalysis of Neutral Precursors in Protic Ionic Liquids and Synthesis of High-Ionicity Ionic Liquids.
Electroanalysis of Neutral Precursors in Protic Ionic Liquids and Synthesis of High-Ionicity Ionic Liquids.
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DOI：
10.1021/acs.langmuir.7b02294
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发表时间：
2017-08
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影响因子：
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通讯作者：
S. Goodwin;Daniel E Smith;Joshua S. Gibson;Robert G. Jones;D. Walsh
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文献类型：
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作者：
S. Goodwin;Daniel E Smith;Joshua S. Gibson;Robert G. Jones;D. Walsh
质子离子液体（pil）是由质子从硼离子酸转移到硼离子碱而形成的离子液体。虽然它们名义上完全由离子组成，但pil通常可以表现得好像它们含有大量的中性物质（分子或离子簇），目前有很多人对确定pil的“离子化”程度感兴趣。在这篇论文中，我们描述了一种简单的电分析方法，用于检测和定量一系列氨基PILs（二乙基甲基三氟酸铵[dema][TfO]、二甲基乙基三氟酸铵[dmea][TfO]、三氟乙酸三乙基铵[tea][TfAc]和三氟酸二甲基丁铵[dmba][TfO]）中残留的过量酸。超微电极伏安法表明，一些公认的合成pil的方法可以很容易地形成非化学计量的pil，其中含有高达230 mM的过量酸。此外，在非化学计量颗粒形成的情况下，真空净化颗粒的用途有限。虽然在环境条件下可以很容易地从pil中去除多余的碱，但即使在高真空条件下也不能去除多余的酸。研究了过量酸对PIL中电催化氧还原反应（ORR）的影响，发现在PIL中加入酸后，[dema][TfO]中ORR的起始电位提高了0.8 V。在分析结果的基础上，对高离子型高分子聚合物的合成提出了建议。
Protic ionic liquids (PILs) are ionic liquids that are formed by transferring protons from Brønsted acids to Brønsted bases. While they nominally consist entirely of ions, PILs can often behave as though they contain a significant amount of neutral species (either molecules or ion clusters), and there is currently a lot of interest in determining the degree of "ionicity" of PILs. In this contribution, we describe a simple electroanalytical method for detecting and quantifying residual excess acids in a series of ammonium-based PILs (diethylmethylammonium triflate [dema][TfO], dimethylethylammonium triflate [dmea][TfO], triethylammonium trifluoroacetate [tea][TfAc], and dimethylbutylammonium triflate [dmba][TfO]). Ultra-microelectrode voltammetry reveals that some of the accepted methods for synthesizing PILs can readily result in the formation of nonstoichiometric PILs containing up to 230 mM excess acid. In addition, vacuum purification of PILs is of limited use in cases where nonstoichiometric PILs are formed. Although excess bases can be readily removed from PILs under ambient conditions, excess acids cannot be removed, even under high vacuum. The effects of excess acid on the electrocatalytic oxygen reduction reaction (ORR) in PILs have been studied, and the onset potential of the ORR in [dema][TfO] increases by 0.8 V upon addition of acid to PIL. On the basis of the results of our analyses, we provide some recommendations for the synthesis of highly ionic PILs.