Double Layer Structure of Ionic Liquids at the Au(111) Electrode Interface: An Atomic Force Microscopy Investigation
Double Layer Structure of Ionic Liquids at the Au(111) Electrode Interface: An Atomic Force Microscopy Investigation
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DOI：
10.1021/jp200544b
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发表时间：
2011-04-14
影响因子：
3.7
通讯作者：
Atkin, Rob
中科院分区：
文献类型：
--
作者：
Hayes, Robert;Borisenko, Natalia;Atkin, Rob
利用原子力显微镜对两种离子液体(1 -丁基-1-甲基吡啶吡啶三（五氟乙基）三氟磷酸盐（[Py-1,Py-4]FAP）和1-乙基-3-甲基咪唑三（五氟乙基）三氟磷酸盐（[EMIm]FAP）在极化Au（111）电极界面上的双层结构进行了探测。力分离剖面表明，在通电的Au(111)-IL界面上存在多层形态，在高电位下检测到更多的近表面层。在（略负的）开路电位处，存在多个离子层，与Au（111）表面接触的最内层由于静电吸附而富集阳离子。当施加负电极电位（-1.0 V, -2.0 V）时，检测到更强的IL近表面结构：离子层的数量和破裂这些层所需的力都增加了。正极电位（+1.0 V, +2.0 V）也能增强IL近表面结构，但不如负极电位强，因为表面吸附的阴离子在后续层的模板结构中不如阳离子有效。这种界面结构不符合Stern-Gouy-Chapman意义上的双层结构，因为没有弥散层。结构符合电容双层模型，电荷面之间的分离距离非常小。
The double layer structure of two ionic liquids (ILs), 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl) trifluorophosphate ([Py-1,Py-4]FAP) and 1-ethyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate ([EMIm]FAP) at the polarized Au(111) electrode interface is probed using Atomic Force Microscopy force measurements. The force-separation profiles suggest a multilayered morphology is present at the electrified Au(111)-IL interface, with more near surface layers detected at higher potentials. At the (slightly negative) open circuit potential, multiple ion layers are present, and the innermost layer, in contact with the Au(111) surface, is enriched in the cation due to electrostatic adsorption. Upon applying negative electrode potentials (-1.0 V, -2.0 V), stronger IL near surface structure is detected: both the number of ion layers and the force required to rupture these layers increases. Positive electrode potentials (+1.0 V, +2.0 V) also enhance IL near surface structure, but not as much as negative potentials, because surface-adsorbed anions are less effective at templating structure in subsequent layers than cations. This interfacial structure is not consistent with a double layer in the Stern-Gouy-Chapman sense, as there is no diffuse layer. The structure is consistent with a capicitative double-layer model, with a very small separation distance between the planes cif charge.