Effect of Water on the Electrochemical Window and Potential Limits of Room-Temperature Ionic Liquids
Effect of Water on the Electrochemical Window and Potential Limits of Room-Temperature Ionic Liquids
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DOI：
10.1021/je800678e
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发表时间：
2008-12-01
期刊：
影响因子：
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通讯作者：
Compton, Richard G.
中科院分区：
文献类型：
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作者：
O'Mahony, Aoife M.;Silvester, Debbie S.;Compton, Richard G.
采用卡尔费希尔滴定法和循环伏安法研究了室温离子液体（RTILs）中含水量的影响：三（对己基）四烷基三氟三（五氟乙基）磷酸盐[P(14,6,6,6)][NTf(2)]、n -丁基- n -甲基吡啶二（三氟甲基磺酰基）亚胺[C(4)mpyrr][NTf(2)]、1-己基-3-甲基咪唑三（全氟乙基）三氟磷酸盐[C(6)mim][FAP]、1-丁基-甲基咪唑二（三氟甲基磺酰基）亚胺[C(4)mim][NTf(2)]、1-丁基-3-甲基咪唑二（三氟甲基磺酰基）亚胺[C(4)mim][NTf(2)]、N-己基三乙基二（三氟甲基磺酰基）亚胺[N(6,2,2,2)][NTf(2)]， 1-丁基-3-甲基咪唑六氟磷酸盐[C(4)mim][PF(6)], F6]， 1-乙基-3-甲基咪唑二（三氟甲基磺酰基）亚胺[C(2)][NTf(2)]， 1-丁基-3-甲基咪唑四氟硼酸盐[C(4)mim][BF(4)]， 1-己基-3-甲基咪唑碘化物[C(4)mim][I]， 1-丁基-3-甲基咪唑三氟甲基磺酸盐[C(4)mim][OTf]和1-己基-3-甲基咪唑氯[C(6)mim][Cl]。此外，总结了RTILs的电化学相关性能，如粘度、电导率、密度和熔点，并对其进行了讨论。卡尔费雪滴定法用于测定真空干燥、常压和湿样品的RTILs的含水量。特别是阴离子被发现会影响水的吸收水平。阴离子的疏水性遵循以下趋势：[FAP](-) > [NTf(2)](-) > [PF(6)](-) > [BF(4)](-) >卤化物。循环伏安法表明，随着水含量的增加，各离子液体的电化学窗口明显缩小。电化学窗口的减小顺序为：真空干燥>常压>在298 K时变湿> 318 K > 338 K。在真空干燥和常压条件下，还列出了相对于二茂铁内部基准的阳极和阴极电位。所获得的数据可以帮助选择在电化学应用中用作溶剂的RTIL。
The effect of water content on room-temperature ionic liquids (RTILs) was studied by Karl Fischer titration and cyclic voltammetry in the following ionic liquids: tris(P-hexyl)tetradecylphosphonium trifluorotris(pentafluoroethyl)phosphate [P(14,6,6,6)][NTf(2)], N-butyl-N-methyl-pyrrolidinium bis(trifluoromethylsulfonyl)imide [C(4)mpyrr][NTf(2)], 1-hexyl-3-methylimidazolium tris(perfluoroethyl)trifluorophosphate [C(6)mim][FAP], 1-butyl3-methylimidazolium bis(trifluoromethylsulfonyl)imide [C(4)mim][NTf(2)], 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [C(4)dmim][NTf(2)], N-hexyltriethylammonium bis(trifluoromethylsolfonyl)imide [N(6,2,2,2)][NTf(2)], 1-butyl-3-methylirnidazolium hexafluorophosphate [C(4)mim][PF(6)], F6], 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [C(2)mim][NTf(2)], 1-butyl-3-methylimidazolium tetrafluoroborate [C(4)mim][BF(4)], 1-hexyl-3-methylimidazolium iodide [C(4)mim][I], 1-butyl-3-methylimidazolium trifluoromethylsulfonate [C(4)mim][OTf], and 1-hexyl-3-methylimidazolium chloride [C(6)mim][Cl]. In addition, electrochemically relevant properties such as viscosity, conductivity, density, and melting point of RTILs are summarized from previous literature and are discussed. Karl Fisher titrations were carried out to determine the water content of RTILs for vacuum-dried, atmospheric, and wet samples. The anion in particular was found to affect the level of water uptake. The hydrophobicity of the anions adhered to the following trend: [FAP](-) > [NTf(2)](-) > [PF(6)](-) > [BF(4)](-) > halides. Cyclic voltammetry shows that an increase in water content significantly narrows the electrochemical window of each ionic liquid. The electrochemical window decreases in the following order: vacuum-dried > atmospheric > wet at 298 K > 318 K > 338 K. The anodic and cathodic potentials vs ferrocene internal reference are also listed under vacuum-dried and atmospheric conditions. The data obtained may aid the selection of a RTIL for use as a solvent in electrochemical applications.