Characterization of molecular diffusion in electrolyte systems

电解质系统中分子扩散的表征

• 批准号: 460790884
• 负责人: Professor Dr.-Ing. Andreas Paul Fröba
• 金额: --
• 依托单位: Erlangen Graduate School in Advanced Optical Technologies (SAOT)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/460790884?language=en
• 关键词: Characterization; molecular; diffusion; electrolyte; systems

The proposed research project should contribute to a fundamental understanding of the diffusive mass transport in electrolyte systems. For this purpose, dynamic light scattering (DLS) experiments and equilibrium molecular dynamics (EMD) simulations should be further developed and used to characterize the diffusive mass transport in systematically selected systems. Besides molecular diffusion, also cluster diffusion can be present in electrolytes. Raman spectroscopy should be applied simultaneously with DLS and combined with EMD simulations to study the formation of clusters and their influence on molecular diffusion. For the determination of mass diffusivities, DLS analyzes microscopic concentration fluctuations present in fluids at macroscopic thermodynamic equilibrium. The temporal behavior of these fluctuations is governed by the molecular diffusion coefficient and the translational diffusion coefficient of clusters. By EMD simulations, the molecular diffusion coefficients can be accessed by investigating fluctuations on a nanometer scale. Here, the Maxwell-Stefan diffusion coefficient and the thermodynamic factor are calculated and combined to access the Fick diffusion coefficients directly measured by DLS. Furthermore, EMD simulations allow to evaluate the influence of the strong long-range intermolecular electrostatic interactions present in electrolytes on diffusion. While the DLS results are used to verify the EMD simulations, the combination of both methods with Raman scattering provides a close insight into the fluid structure. A flexible experimental setup including both light scattering techniques should be developed for the simultaneous and accurate investigation of diffusivities on different time scales and underlying molecular interactions. For gaining comprehensive information on the diffusive mass transport, selected combinations of salts, including ionic liquids, and organic solvents should be studied over broad ranges of temperature and composition. By a systematic variation of the solute and solvent, covering different molecule types and sizes, the influence of their physical characteristics on the diffusive process should be analyzed. While the diffusive mass transport for binary mixtures with three species is characterized by a single diffusion coefficient, the investigations in this research project should also be extended to four-species systems associated with a second-order diffusion coefficient matrix. Furthermore, the reliable database of diffusivities in electrolyte systems obtained from DLS experiments and EMD simulations and the fundamental knowledge gained from all employed methods should contribute to the development of a predictive engineering model for the molecular diffusion in electrolyte systems.

拟议的研究项目应有助于电解质系统中的扩散传质的基本理解。为此目的，动态光散射（DLS）实验和平衡分子动力学（EMD）模拟应进一步发展和用于系统选择的系统中的扩散传质的特征。除了分子扩散之外，在电解质中还可以存在团簇扩散。拉曼光谱应与DLS同时应用，并结合EMD模拟来研究团簇的形成及其对分子扩散的影响。为了确定质量扩散系数，DLS分析了宏观热力学平衡下流体中存在的微观浓度波动。这些波动的时间行为是由分子扩散系数和集团的平移扩散系数。通过EMD模拟，可以通过研究纳米尺度上的波动来获得分子扩散系数。在这里，Maxwell-Stefan扩散系数和热力学因子的计算和组合访问的菲克扩散系数直接测量DLS。此外，EMD模拟允许评估存在于电解质中的强长程分子间静电相互作用对扩散的影响。 虽然DLS结果被用来验证EMD模拟，这两种方法与拉曼散射的组合提供了一个密切的洞察到流体结构。一个灵活的实验装置，包括两个光散射技术应开发的同时和准确的调查扩散系数在不同的时间尺度和潜在的分子相互作用。为了获得关于扩散传质的全面信息，应在宽的温度和组成范围内研究盐（包括离子液体）和有机溶剂的选定组合。通过溶质和溶剂的系统变化，涵盖不同的分子类型和尺寸，应该分析它们的物理特性对扩散过程的影响。虽然三种二元混合物的扩散传质的特点是由一个单一的扩散系数，在这个研究项目的调查也应扩展到四种物质的系统与二阶扩散系数矩阵。此外，从DLS实验和EMD模拟获得的电解质系统中的扩散系数的可靠数据库和从所有采用的方法获得的基本知识，应有助于电解质系统中的分子扩散的预测工程模型的发展。