Chen Zhichao, Li Zixuan, Zhao Wei, Matsumoto Ray A, Thompson Matthew W, Morales-Collazo Oscar, Cummings Peter T, Mangolini Filippo, Brennecke Joan F
McKetta Department of Chemical Engineering, The University of Texas at Austin, Austin, Texas 78712, United States.
Texas Materials Institute, The University of Texas at Austin, Austin, Texas 78712, United States.
Langmuir. 2022 Apr 5;38(13):4036-4047. doi: 10.1021/acs.langmuir.2c00024. Epub 2022 Mar 21.
The molecular-level orientation and structure of ionic liquids (ILs) at liquid-solid interfaces are significantly different than in the bulk. The interfacial ordering influences both IL properties, such as dielectric constants and viscosity, and their efficacy in devices, such as fuel cells and electrical capacitors. Here, we report the layered structures of four ILs on unbiased, highly ordered pyrolytic graphite (HOPG) and Pt(111) surfaces, as determined by atomic force microscopy. The ILs investigated are 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([emim][TfN]), 1-ethyl-3-methylimidazolium perfluorobutylsulfonate ([emim][CFSO]), 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene bis(trifluoromethylsulfonyl)imide ([MTBD][TfN]), and 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene perfluorobutylsulfonate ([MTBD][CFSO]). Molecular dynamics simulations provide complementary information on the position and orientation of the ions. These ILs form a cation layer at the IL-solid interface, followed by a layer of anions. [Emim] and [MTBD] have similar orientations at the surface, but [MTBD] forms a thinner layer compared to [emim] on both HOPG and Pt(111). In addition, [TfN] shows stronger interactions with Pt(111) surfaces than [CFSO].
离子液体（ILs）在液固界面的分子水平取向和结构与本体中的显著不同。界面有序性既影响离子液体的性质，如介电常数和粘度，也影响其在燃料电池和电容器等器件中的效能。在此，我们报告了通过原子力显微镜测定的四种离子液体在无偏、高度有序的热解石墨（HOPG）和Pt(111)表面的层状结构。所研究的离子液体为1-乙基-3-甲基咪唑双（三氟甲基磺酰）亚胺（[emim][TfN]）、1-乙基-3-甲基咪唑全氟丁磺酸盐（[emim][CFSO]）、7-甲基-1,5,7-三氮杂双环[4.4.0]癸-5-烯双（三氟甲基磺酰）亚胺（[MTBD][TfN]）和7-甲基-1,5,7-三氮杂双环[4.4.0]癸-5-烯全氟丁磺酸盐（[MTBD][CFSO]）。分子动力学模拟提供了关于离子位置和取向的补充信息。这些离子液体在IL-固体界面形成一个阳离子层，随后是一层阴离子。[Emim]和[MTBD]在表面具有相似的取向，但与HOPG和Pt(111)上的[emim]相比，[MTBD]形成的层更薄。此外，[TfN]与Pt(111)表面的相互作用比[CFSO]更强。
