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（RTILs）是一种纯离子溶剂，其电位窗口为3 ~ 6 V)的性质对其作为电化学系统的电解质、复杂氧化还原反应研究的溶剂或超级电容器的应用具有很大的吸引力。在传统介质中，溶剂分子和支撑电解质的离子与电极直接接触，而在RTILs中，只有离子存在于电极表面。与电化学中常用的溶剂相比，它会影响RTILs双电层的宏观电化学性能和结构。尽管在亚分子水平上对RTILs双电层的结构知之甚少，但对RTILs双电层的原位研究非常罕见。本课题将利用电化学和极化调制红外反射吸收光谱（PM IRRAS）研究电化学控制下RTILs双电层的结构。根据最近的发现（Kirchner et al., Electrochim.Acta.）。RTILs双电层的超分子结构取决于施加在电极上的电位，并且从多层到单层组件各不相同。本课题将在Au和Pt电极表面制备模拟RTILs双电层组成和结构的Langmuir-Blodgett （LB）薄膜。研究了LB膜在水溶液和RTIL溶液中的电化学吸附电位窗口、零电荷电位和表面电荷电位作为电极电位的函数。电化学控制下的PM IRRAS将用于研究施加在电极上的电位对模型RTIL|电极界面上阴离子和阳离子结构和取向的影响。接下来，原位PM IRRAS将用于研究纯RTILs电双层中离子结构和取向的电位驱动变化。区分本体液相中RTIL离子与电极表面吸附离子的红外吸收信号是本研究项目的主要挑战。只有在这样的光谱电化学电池设置中，p偏振光的强度（带来电极表面和样品（电解质）环境中吸附的离子的信息）和s偏振光的强度（带来样品环境的信息）是相同的，才有可能。这种智能的实验方法确保了本项目的成功实现，并扩大了PM IRRAS作为结构和表面分析技术的适用性。

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.