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

当盐溶于水时，它们会形成电解质。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发挥着重要作用，并被用于电化学储能技术。虽然人们对平面附近的EDL的结构和性质都很了解，但对纳米孔道材料中的EDL的了解却很少。这些纳米多孔材料对电化学储能应用很感兴趣，这也是该项目的动机。特别是，EDL在纳米多孔材料中的形成会产生机械应力，导致材料变形。本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相关联。从这项研究中获得的知识可能有助于开发新的电化学储能设备，如采用绿色水基电解液的超级电容器，以及基于电化学原理的致动器。该项目将通过将与研究有关的主题纳入该大学教授的本科课程，促进改善STEM教育。在夏季的几个月里，高中实习生将从事与这项研究相关的项目。本研究项目的目的是应用微观和宏观尺度的实验和分子模拟来获得对纳米孔介质中EDL的机电性质的基本了解。具有高比表面积、定义良好的孔径(1-10 nm)和孔几何形状的导电纳米多孔炭将被合成。不同的表面化学(疏水和亲水)将被介绍。根据电解液和固体之间施加的电压，将研究材料的表面化学和孔径、EDL的形成和机械驱动。基于同步加速器的X射线散射将被用来研究EDL在操作中，特别是注意充放电和离子输运动力学。分子动力学模拟将被用来表示纳米孔介质和电解液表面的结构性质。结合实验(德国团队)和模拟(美国团队)将有助于得出几何受限电解液的结构、热力学和传输性质，以及它们在单孔和整个多孔样品尺度上对电化学-机械耦合的作用。除了对几何约束中的水溶液的这些基本见解，这项研究还可能有助于新一代电化学设备的开发。该项目是通过“受限空间中的化学和运输(NSF-DFG Confinit)”机会获得的，这是一个由国家科学基金会和德国科学基金会(DFG)参与的合作征集活动。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.