We studied the adsorption and thermal behavior of the nitrile-functionalized ionic liquid (IL) [C₃CNC₁Im][Tf₂N] on Au(111) and Pt(111) between 150 and 600 K. Ultrathin films were prepared at 150 K by physical vapor deposition (PVD) and were characterized by angle resolved X-ray photoelectron spectroscopy (ARXPS). At 150 K, the IL adsorbs intact with a similar orientation on both surfaces: In the first layer, the so-called wetting layer, the cation lies flat on the surface and the anion is bound in cis-configuration with the SO₂ groups toward the surface and the CF₃ groups away from the surface. On Au(111), subsequent deposition of IL in the multilayer regime at 150 K shows 2D growth up until ∼0.75 ML and a transition to moderate 3D at higher coverages. Temperature-programmed XPS indicates a change in surface morphology toward more pronounced 3D islands for the multilayers on top of the wetting layer between 220 and 290 K. From 350 to 440 K, desorption of multilayers occurs, with IL decomposition starting at 375–400 K. On the more reactive Pt(111) surface, decomposition starts already above 280 K. Notably, this temperature is ∼80 K higher than the onset for decomposition of related nonfunctionalized imidazolium-based ILs, that is, [C₂C₁Im][OTf], [C₁C₁Im][Tf₂N], and [C₈C₁Im][Tf₂N] on Pt(111). This difference is attributed to the nitrile functionality. Our findings demonstrate that functionalizing ILs significantly modifies their thermal properties, which is of high relevance for SCILL (solid catalyst with an ionic liquid layer) systems.

中文翻译：

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丁腈官能团化离子液体 [C3CNC1Im][Tf2N] 在 Au（111） 和 Pt（111） 上的超薄薄膜：吸附、生长和热行为


我们研究了丁腈官能化离子液体 （IL） [C₃CNC₁Im][Tf₂N] 在 150 至 600 K 之间的 Au（111） 和 Pt（111） 上的吸附和热行为。在 150 K 下通过物理气相沉积 （PVD） 制备超薄膜，并通过角度分辨 X 射线光电子能谱 （ARXPS） 表征。在 150 K 时，IL 在两个表面上以相似的方向完整吸附：在第一层，即所谓的润湿层中，阳离子平放在表面上，阴离子以顺式构型结合，SO₂ 基团朝向表面，CF₃ 基团远离表面。在 Au（111） 上，随后在 150 K 的多层结构中沉积 IL 显示 2D 生长至 ∼0.75 ML，并在较高覆盖率下过渡到中等 3D。程序升温 XPS 表明，在 220 和 290 K 之间，润湿层顶部的多层膜的表面形态发生变化，朝着更明显的 3D 岛发展。从 350 到 440 K，发生多层解吸，IL 分解从 375-400 K 开始。值得注意的是，该温度比相关的非功能化咪唑基 IL 的分解开始高 ∼80 K，即 [C₂C₁Im][OTf]、[C₁C₁Im][Tf₂N] 和 [C₈C₁Im][Tf₂N] 在 Pt（111） 上。这种差异归因于丁腈功能。我们的研究结果表明，官能化 IL 会显着改变它们的热特性，这与 SCILL （具有离子液体层的固体催化剂） 系统高度相关。