Zhao Chuan, Burrell Geoff, Torriero Angel A J, Separovic Frances, Dunlop Noel F, MacFarlane Douglas R, Bond Alan M
School of Chemistry, Monash University, Clayton, Victoria 3800, Australia.
J Phys Chem B. 2008 Jun 12;112(23):6923-36. doi: 10.1021/jp711804j. Epub 2008 May 20.
Eighteen protic ionic liquids containing different combinations of cations and anions, hydrophobicity, viscosity, and conductivity have been synthesized and their physicochemical properties determined. In one series, the diethanolammonium cations were combined with acetate, formate, hydrogen sulfate, chloride, sulfamate, and mesylate anions. In the second series, acetate and formate anions were combined with amine bases, triethylamine, diethylamine, triethanolamine, di-n-propylamine, and di-n-butylamine. The electrochemical characteristics of the eight protic ionic liquids that are liquid at room temperature (RTPILs) have been determined using cyclic, microelectrode, and rotating disk electrode voltammetries. Potential windows of the RTPILs have been compared at glassy carbon, platinum, gold, and boron-doped diamond electrodes and generally found to be the largest in the case of glassy carbon. The voltammetry of IUPAC recommended potential scale reference systems, ferrocene/ferrocenium and cobaltocenium/cobaltocene, have been evaluated and found to be ideal in the case of the less viscous RTPILs but involve adsorption in the highly viscous ones. Other properties such as diffusion coefficients, ionic conductivity, and double layer capacitance also have been measured. The influence of water on the potential windows, viscosity, and diffusion has been studied systematically by deliberate addition of water to the dried ionic liquids. The survey highlights the problems with voltammetric studies in highly viscous room temperature protic ionic liquids and also suggests the way forward with respect to their possible industrial use.
已合成了十八种含有不同阳离子和阴离子组合、具有疏水性、粘度和电导率的质子离子液体，并测定了它们的物理化学性质。在一个系列中，二乙醇铵阳离子与醋酸根、甲酸根、硫酸氢根、氯离子、氨基磺酸根和甲磺酸根阴离子结合。在第二个系列中，醋酸根和甲酸根阴离子与胺碱、三乙胺、二乙胺、三乙醇胺、二正丙胺和二正丁胺结合。使用循环伏安法、微电极伏安法和旋转圆盘电极伏安法测定了八种在室温下为液体的质子离子液体（RTPILs）的电化学特性。在玻碳、铂、金和掺硼金刚石电极上比较了RTPILs的电位窗口，通常发现在玻碳电极上电位窗口最大。对国际纯粹与应用化学联合会（IUPAC）推荐的电位标度参考体系二茂铁/二茂铁离子和钴茂/钴茂离子的伏安法进行了评估，发现在低粘度的RTPILs中是理想的，但在高粘度的RTPILs中会涉及吸附。还测量了其他性质，如扩散系数、离子电导率和双层电容。通过有意向干燥的离子液体中加水，系统地研究了水对电位窗口、粘度和扩散的影响。该综述突出了在高粘度室温质子离子液体中进行伏安研究的问题，并也提出了关于它们可能的工业用途的前进方向。
