Xu Tao, Waehler Tobias, Vecchietti Julia, Bonivardi Adrian, Bauer Tanja, Schwegler Johannes, Schulz Peter S, Wasserscheid Peter, Libuda Joerg
Lehrstuhl für Physikalische Chemie II, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058, Erlangen, Germany), Fax: +49 9131 8527308.
Instituto de Desarrollo Tecnológico para la Industria Química (INTEC), UNL-CONICET, Güemes 3450, 3000, Santa Fe, Argentina.
Chemphyschem. 2017 Dec 6;18(23):3443-3453. doi: 10.1002/cphc.201700843. Epub 2017 Oct 13.
Hybrid materials consisting of ionic liquid (ILs) films on supported oxides hold a great potential for applications in electronic and energy materials. In this work, we have performed surface science model studies scrutinizing the interaction of ester-functionalized ILs with atomically defined Co O (111) and CoO(100) surfaces. Both supports are prepared under ultra-high vacuum (UHV) conditions in form of thin films on Ir(100) single crystals. Subsequently, thin films of three ILs, 3-butyl-1-methyl imidazolium bis(trifluoromethyl-sulfonyl) imide ([BMIM][NTf ]), 3-(4-methoxyl-4-oxobutyl)-1-methylimidazolium bis(trifluoromethyl-sulfonyl) imide ([MBMIM][NTf ]), and 3-(4-isopropoxy-4-oxobutyl)-1-methylimidazolium bis(trifluoromethyl-sulfonyl) imide ([IPBMIM][NTf ]), were deposited on these surfaces by physical vapor deposition (PVD). Time-resolved and temperature-programmed infrared reflection absorption spectroscopy (TR-IRAS, TP-IRAS) were applied to monitor in situ the adsorption, film growth, and thermally induced desorption. By TP-IRAS, we determined the multilayer desorption temperature of [BMIM][NTf ] (360±5 K), [MBMIM][NTf ] (380 K) and [IPBMIM][NTf ] (380 K). Upon deposition below the multilayer desorption temperature, all three ILs physisorb on both cobalt oxide surfaces. However, strong orientation effects are observed in the first monolayer, where the [NTf ] ion interacts with the surface through the SO groups and the CF groups point towards the vacuum. For the two functionalized ILs, the [MBMIM] and [IPBMIM] interact with the surface Co ions of both surfaces via the CO group of their ester function. A very different behavior is found, if the ILs are deposited above the multilayer desorption temperature (400 K). While for [BMIM][NTf ] and [MBMIM][NTf ] a molecularly adsorbed monolayer film is formed, [IPBMIM][NTf ] undergoes a chemical transformation on the CoO(100) surface. Here, the ester group is cleaved and the cation is chemically linked to the surface by formation of a surface carboxylate. The IL-derived species in the monolayer desorb at temperatures around 500 to 550 K.
由负载型氧化物上的离子液体（ILs）薄膜组成的杂化材料在电子和能源材料领域具有巨大的应用潜力。在这项工作中，我们进行了表面科学模型研究，仔细考察了酯功能化离子液体与原子级定义的CoO(111)和CoO(100)表面的相互作用。两种载体均在超高真空（UHV）条件下制备成Ir(100)单晶上的薄膜形式。随后，通过物理气相沉积（PVD）将三种离子液体3-丁基-1-甲基咪唑双（三氟甲基磺酰）亚胺（[BMIM][NTf₂]）、3-(4-甲氧基-4-氧代丁基)-1-甲基咪唑双（三氟甲基磺酰）亚胺（[MBMIM][NTf₂]）和3-(4-异丙氧基-4-氧代丁基)-1-甲基咪唑双（三氟甲基磺酰）亚胺（[IPBMIM][NTf₂]）的薄膜沉积在这些表面上。采用时间分辨和程序升温红外反射吸收光谱（TR-IRAS、TP-IRAS）原位监测吸附、薄膜生长和热诱导解吸。通过TP-IRAS，我们确定了[BMIM][NTf₂]（360±5 K）、[MBMIM][NTf₂]（380 K）和[IPBMIM][NTf₂]（380 K）的多层解吸温度。在低于多层解吸温度下沉积时，所有三种离子液体都在两种氧化钴表面发生物理吸附。然而，在第一单层中观察到强烈的取向效应，其中[NTf₂]离子通过-SO₂基团与表面相互作用，而-CF₃基团指向真空。对于两种功能化离子液体，[MBMIM]和[IPBMIM]通过其酯功能的-CO基团与两种表面的表面Co离子相互作用。如果离子液体在多层解吸温度（400 K）以上沉积，则会发现非常不同的行为。虽然对于[BMIM][NTf₂]和[MBMIM][NTf₂]形成了分子吸附的单层薄膜，但[IPBMIM][NTf₂]在CoO(100)表面发生化学转变。在这里，酯基被裂解，阳离子通过形成表面羧酸盐与表面化学连接。单层中的离子液体衍生物种在500至550 K左右的温度下解吸。
