In situ spectroelectrochemical studies of potential driven changes in the structure of the electrical double layer at the ionic liquid|electrode interface

室温离子液体（RTIL）是一种纯的离子溶剂，其电位窗口为3-6 V，在电化学体系中作为电解质、复杂氧化还原反应的研究溶剂以及超级电容器等方面具有广泛的应用前景。与其中溶剂分子和支持电解质的离子与电极直接接触的常规介质相比，在RTIL中仅离子存在于电极表面上。与电化学中常用的溶剂相比，它影响RTIL的宏观电化学性质和双电层结构。尽管在亚分子水平上对RTIL的双电层结构知之甚少，但对RTIL双电层的原位研究非常罕见。在这个项目中，RTIL的双电层的结构将使用电化学和偏振调制红外反射吸收光谱（PM IRRAS）电化学控制下进行研究。根据最近的发现（Kirchner等人，电化学学报，110，2013，762），RTIL的电双层的超分子结构取决于施加到电极的电势，并且从多层到单层组件变化。在本项目中，将在Au和Pt电极表面制备模拟RTIL双电层组成和结构的LB膜。研究了LB膜在水溶液和RTIL溶液中吸附的电化学电位窗口、零电荷电位和表面电荷随电极电位的变化关系。电化学控制下的PM IRRAS将用于研究施加到电极上的电势对模型RTIL中阴离子和阳离子的结构和取向的影响|电极界面接下来，在原位PM IRRAS将被用来调查的纯RTIL的双电层中的离子的结构和取向的潜在驱动的变化。本研究项目的主要挑战是区分来自吸附在电极表面上的离子的本体液相中存在的RTIL离子的IR吸收信号。仅对于其中p偏振光的强度（带来关于吸附在电极表面和样品环境（电解质）中的离子的信息）和s偏振光的强度（带来关于样品环境的信息）相同的光谱电化学池的这种设置是可能的。这种巧妙的实验方法保证了该项目的成功实现，扩大了PM IRRAS作为结构和表面分析技术的适用范围。

The properties of room-temperature ionic liquids ((RTILs), a pure ionic solvent with potential window of 3-6 V) are very attractive for their applications as electrolytes in electrochemical systems, as solvents for studies of complex redox reactions or as supercapacitors. By contrast to conventional media in which molecules of a solvent and ions of a supporting electrolyte are in a direct contact with an electrode, in RTILs only ions are present on the electrode surface. It influences the macroscopic electrochemical properties and structure of the electrical double layer of RTILs comparing to solvents commonly used in electrochemistry. Despite the fact that little is known about the structure of the electrical double layer of RTILs at a sub-molecular level, in situ studies of the electrical double layer of RTILs are very rare. In this project the structure of the electrical double layer of RTILs will be studied using electrochemistry and polarization modulation infrared reflection-absorption spectroscopy (PM IRRAS) under electrochemical control. According to recent findings (Kirchner et al., Electrochim.Acta.,110,2013,762) the supramolecular structure of the electrical double layer of RTILs depends on the potential applied to the electrode and varies from multilayer to monolayer assemblies. In this project Langmuir-Blodgett (LB) films mimicking the composition and structure of the electrical double layer of RTILs will be prepared on the surface of Au and Pt electrodes. Electrochemical potential window of the film adsorption, potential of zero charge and surface charge as the function of the electrode potential will be studied in LB films in aqueous and RTIL solutions. PM IRRAS under electrochemical control will be used to study impact of the potential applied to the electrode on the structure and orientation of anions and cations at the model RTIL|electrode interface. Next, in situ PM IRRAS will be used to investigate potential-driven changes in the structure and orientation of ions in the electrical double layer of pure RTILs. A differentiation of the IR absorption signals from the RTIL ions present in the bulk liquid phase from the ions adsorbed on the electrode surface is the main challenge of this research project. It will be possible only for such settings of the spectroelectrochemical cell in which the intensity of the p-polarized light (brings information on the ions adsorbed in the electrode surface and in the environment of the sample (electrolyte)) and the intensity of the s-polarized light (brings information about the environment of the sample) are the same. This smart experimental approach ensures a successful realization of this project and enlarges the applicability of the PM IRRAS as structure and surface analyzing technique.