Voltage-dependent interfacial structure and properties of room temperature ionic liquids: operando X-ray studies

在这个由化学部化学结构动力学和机制（CSDM-A）计划资助的项目中，西北大学的Pulak Dutta教授正在使用来自同步辐射源的X射线来研究纯粹由分子离子组成的液体（称为室温离子液体或RTIL）。 这些新型液体已被提出用于多种应用，例如电池和超级电容器中的电解质、溶剂等，并且它们具有许多与更通常已知的水基液体电解质的性质完全不同的性质。 这些不寻常的性质的纳米起源研究如何离子安排自己附近的电极时，施加可变电压，以及这些安排如何发展和随着时间的变化。 这些研究将开发必要的知识，不仅要了解RTIL的观察特性，而且最终要设计和控制这些行为。本项目主要研究室温离子液体（RTIL），它是一种含有分子阴离子和/或分子阳离子的熔盐，目的是实验研究RTIL离子在电极界面附近的静态和动态排列对电场的响应;将这种行为与RTIL中存在的离子的分子结构相关联;并试图理解结构如何确定或影响所观察到的电化学和电润湿性质。主要的实验探头是在原位X射线反射率和掠入射X射线衍射从固体RTIL接口，使用国家同步加速器设施。 的界面结构和它的动力学上存在的离子，电极表面的性质，并施加的直流和交流电压的依赖性，正在研究和现有的理论预测相比。 预期的结果是一个更好的基本了解RTIL的纳米级界面行为，从而提高了知识如何选择或设计离子液体，以优化所需的性能，为实际应用。

In this project funded by the Chemical Structure Dynamics and Mechanisms (CSDM-A) program of the Chemistry Division, Prof. Pulak Dutta of Northwestern University is using X-rays from synchrotron radiation sources to study liquids composed purely of molecular ions (known as room-temperature ionic liquids, or RTILs). These novel liquids have been proposed for a variety of applications such as electrolytes in batteries and supercapacitors, solvents, etc., and they have a number of properties that are quite different from those of more commonly known water-based liquid electrolytes. The nanoscale origins of these unusual properties are investigated by studying how the ions arrange themselves near electrodes when variable voltages are applied, and how these arrangements develop and change with time. These studies will develop the knowledge necessary to not just understand the observed properties of RTILs, but ultimately to design and control these behaviors. This would potentially allow improved batteries and capacitors, easy ways to manipulate small droplets in microfluidic systems, etc.This project focuses on room-temperature ionic liquids (RTILs), which are molten salts with molecular anions and/or molecular cations The objectives are to study experimentally how the static and dynamic arrangements of RTIL ions near electrode interfaces respond to electric fields; to correlate this behavior with the molecular structures of the ions present in the RTIL; and to seek to understand how the structures determine or affect the observed electrochemical and electrowetting properties. The primary experimental probe is in situ X-ray reflectivity and grazing incidence X-ray diffraction from solid-RTIL interfaces, using national synchrotron facilities. The dependence of the interfacial structure and its dynamics on the ions present, the nature of the electrode surface, and on applied direct and alternating voltages, are being studied and compared to existing theoretical predictions. The anticipated outcome is a better fundamental understanding of the nanoscale interfacial behavior of RTILs, and thus improved knowledge of how to select or design ionic liquids in order to optimize desired properties for practical applications.