NSF-DFG Confine: Aqueous Electrolytes in Nanoporous Media: Structure, Dynamics and Electrochemo-Mechanical Actuation

当盐溶解在水中时，它们形成电解质。在带电固体表面附近，电解质中的离子重新分布，形成双电层（EDL）。EDL在地球化学和生物过程中起着重要作用，并用于电化学储能技术。虽然对于靠近平面表面的EDL，已经很好地理解了EDL的结构和性质，但是对纳米多孔材料中的EDL的理解很差。这些纳米多孔材料对电化学储能应用感兴趣，这激发了这个项目。特别地，纳米多孔材料中的EDL形成引起机械应力并导致材料变形。该研究项目旨在量化纳米多孔材料中电解质水溶液中EDL的形成，并将其与这些材料中的应力和应变联系起来。从这项研究中获得的知识可以有助于开发新的电化学能量存储设备，例如具有绿色水基电解质的超级电容器，以及基于电化学原理的致动器。该项目将通过在大学教授的本科课程中纳入与研究相关的主题，为改善STEM教育做出贡献。在夏季的几个月里，高中实习生将从事与这项研究有关的项目。本研究项目的目的是应用微观和宏观尺度的实验沿着分子模拟，以获得纳米多孔介质中的EDL的机电性能的基本理解。将合成具有高比表面积、良好限定的孔径（1-10 nm）和孔几何形状的导电纳米多孔碳。将引入不同的表面化学（疏水与亲水）。根据电解质和固体之间施加的电压，材料的表面化学和孔径，EDL形成和机械致动将被研究。基于同步加速器的X射线散射将被用来研究在操作中的EDL，特别注意的充电/放电，从而离子传输动力学。将采用分子动力学模拟来表示纳米多孔介质和电解质的表面的结构性质。实验（德国团队）和模拟（美国团队）的结合将有助于推导出几何限制电解质的结构，热力学和传输特性及其在单个孔和整个多孔样品尺度上的电化学-机械耦合作用。除了这些基本的见解水电解质的几何约束，这项研究可能有助于开发新一代的电化学设备。（NSF-DFG限制）”机会，一项涉及美国国家科学基金会和德国研究共同体（DFG）的合作征集活动该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

When salts dissolve in water, they form electrolytes. Near a charged solid surface ions in an electrolyte redistribute, forming an electric double layer (EDL). EDL plays an important role in geochemical and biological processes and is utilized in technologies for electrochemical energy storage. While the structure and properties of EDL are well understood for an EDL near a planar surface, understanding of EDL in nanoporous materials is poor. These nanoporous materials are of interest for electrochemical energy storage applications, which motivates this project. In particular EDL formation in nanoporous materials causes mechanical stresses and lead to materials deformation. This research project aims to quantify the formation of EDL in aqueous solutions of electrolytes in nanoporous materials and relate it to stresses and strains in these materials. The knowledge gained from this research could contribute towards developing new electrochemical energy storage devices, such as supercapacitors with green, water-based electrolytes, as well as actuators based on electrochemical principles. This project will contribute to improved STEM education through the inclusion of research related topics in the undergraduate courses taught at the university. During the summer months high school interns will work on projects related to this research. The objective of this research project is to apply experiments on the micro- and macroscale along with molecular simulations to gain fundamental understanding of the electromechanical properties of an EDL in nanoporous media. Electrically conducting nanoporous carbons with high specific surface area, well-defined pore sizes (1-10 nm) and pore geometries will be synthesized. Different surface chemistries (hydrophobic vs. hydrophilic) will be introduced. Depending on the applied electrical voltage between electrolyte and solid, the surface chemistry and the pore diameter, EDL formation and mechanical actuation in the material will be investigated. Synchrotron-based X-ray scattering will be used to study the EDL in-operando, with special attention to the charge/discharge and thus ion transport kinetics. Molecular dynamics simulations will be employed to represent the structural properties of the surface of the nanoporous medium and the electrolyte. Combination of experiments (German team) and simulations (US team) will help to derive the structural, thermodynamic and transport properties of the geometrically confined electrolyte and their role for electrochemo-mechanical coupling at the scale of a single pore and the entire porous sample. In addition to these fundamental insights into aqueous electrolytes in geometric confinement, this study can potentially contribute to development of new generations of electrochemical devices.This project was awarded through the “Chemistry and Transport in Confined Spaces (NSF-DFG Confine)" opportunity, a collaborative solicitation that involves the National Science Foundation and Deutsche Forschungsgemeinschaft (DFG).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.