Collaborative Research: Ion Mobility in Aqueous Acids, Bases, and Salts

在化学系化学结构，动力学和机制-A（CSDM-A）计划的支持下，由圣母大学的Steven Corcelli教授和宾夕法尼亚州立大学的Paul Cremer教授领导的研究小组正在研究离子在水中的流动性，并采用完全集成的实验和理论建模方法。含有盐的溶液，包括酸和碱，在许多化学、生物和环境过程中是必不可少的，并且离子传输速率与采用水性电解质的新兴电池技术特别相关。然而，离子传输的详细分子机制，包括抗衡离子和离子配对的作用，还没有完全理解。因此，本项目的研究目标是在分子水平上探索离子在水中的迁移率，以统一理解抗衡离子和离子配对对水溶液中酸、碱和盐的离子传输结构、动力学和机制的作用。除了这项工作的更广泛的科学影响外，该项目还包括为研究生和本科生提供高级培训机会，以及为高中生开发相关的实验室实验。初步研究结果表明，抗衡离子大大影响氢氧化物的流动性，离子配对效应是中央的酸，碱，盐的流动性。该项目涉及系统地研究霍夫迈斯特系列离子在酸，碱和盐溶液中作为浓度的函数。实验上，扩散常数测量电化学阻抗谱，和拉曼和红外光谱的组合阐明有关离子结构，水合作用，质子离域的信息。互补核磁共振光谱测量产生质子转移速率和有关单个离子迁移率的信息。理论上，酸和碱用从头算分子动力学模拟，盐用分子动力学模拟。基于模拟的计算提供了相应的离子对之间的关联的自由能，并帮助解释实验拉曼和红外光谱。光谱和模拟研究协同联合收割机提供了一个分子水平的理解扩散常数测量。结合的研究阐明的Grotthuss机制的质子跳跃和特定的作用的溶剂共享与接触离子配对在电解质水溶液中的抗衡离子的影响。这项工作的更广泛影响包括更好地理解离子迁移率对许多技术应用的重要性，高级学生培训机会，以及开发和实施高中实验室实验，探索疏水界面的离子配对。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估来支持。

With support from the Chemical Structure, Dynamics, and Mechanisms-A (CSDM-A) Program in the Division of Chemistry, a research team led by Professors Steven Corcelli at the University of Notre Dame and Paul Cremer at Pennsylvania State University is investigating the mobility of ions in water with a fully integrated experimental and theoretical modeling approach. Solutions containing salt, including acids and bases, are essential in many chemical, biological, and environmental processes, and the rates of ion transport are especially relevant to emerging battery technologies employing aqueous electrolytes. However, the detailed molecular mechanism for ion transport, including the role of counterions and ion-pairing, is not fully understood. Thus, the research objective of this project is to explore ionic mobility in water at the molecular level to achieve a unified understanding of the role of counterions and ion-pairing on the structure, dynamics, and mechanisms of ion transport in aqueous acids, bases, and salts. In addition to the broader scientific impacts of the work, the project also includes advanced training opportunities for graduate and undergraduate students, as well as the development of a related laboratory experiment for high school students. Preliminary findings that counterions substantially impact hydroxide mobility suggest that ion-pairing effects are central to acid, base, and salt mobility. This project involves a systematic study of Hofmeister series ions in acid, base, and salt solutions as a function of concentration. Experimentally, diffusion constants are measured by electrochemical impedance spectroscopy, and a combination of Raman and infrared spectroscopy elucidate information about ion structure, hydration, and proton delocalization. Complementary nuclear magnetic resonance spectroscopy measurements yield proton transfer rates and information about the mobility of individual ions. Theoretically, the acids and bases are simulated with ab initio molecular dynamics and the salts with molecular dynamics. Calculations based on the simulations provide the free energy of association between respective ion pairs and aid the interpretation of the experimental Raman and infrared spectra. The spectroscopic and simulation studies synergistically combine to provide a molecular-level understanding of diffusion constant measurements. The combined studies elucidate the impact of counterions on the Grotthuss mechanism of proton hopping and the particular roles of solvent-shared versus contact ion-pairing in aqueous electrolyte solutions. The broader impacts of the work include the importance of better understanding ion mobility for many technological applications, advanced student training opportunities, and development and implementation of a high school laboratory experiment that explores ion-pairing at hydrophobic interfaces.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.