Collaborative Research: Understanding and Tuning the Molecular Arrangement and Charge Storage Properties of Textured Graphene-Ionic Liquid Interface

非技术概述随着电力需求的不断增长，下一代储能设备(电池和超级电容器)的设计必须能够支持比当前技术更高的能量密度。因此，必须探索新的电解液和电极材料，以允许更高的电解液填充密度。为了改善电极/电解液界面，该项目在NSF材料研究部固态和材料化学计划的支持下，试图了解如何通过精确控制纳米尺度上的电极几何来调节离子液体的结构及其在电极界面的排列。单层石墨烯是一种碳基材料，只有一个原子厚，可以用作高度灵活的导电电极，用于本研究的纹理电极。研究小组调查了电极形态对离子液体电解液组织的影响，以及它如何影响电荷存储。除了探索这些基础科学问题外，该项目还支持材料和表面科学交叉领域来自不同背景的本科生和研究生的教育和培训，通过在UIUC和TAMU首席研究员实验室之间的协调合作环境中培训学生进行交叉研究，为美国能源部门劳动力的发展做出贡献。技术概述在NSF材料研究部固态和材料化学计划的支持下，首席研究员(UIUC的Epinosa-Marzal和TAMU的Batteas)测试了基本假设，即通过控制表面形貌和衬底诱导的电荷掺杂，以及离子液体的化学组成，可以精确地调节液体在石墨烯上的局部堆积密度。这反过来有望提供对其电荷存储特性的更好控制。为了填补概述的知识空白，该团队进行了三条主要的研究路线。发展了一种新的制备石墨烯表面的方法，这种表面具有精确控制的电荷掺杂和从原子到纳米尺度的形貌。此外，在电化学池中用原子力显微镜研究了衬底形貌和电荷掺杂对离子液体界面结构和双电层特性的影响。此外，还使用局部和全局电化学阻抗谱将双电层与织构界面的微分电容联系起来。这些研究可以确定石墨烯粗糙度、电荷掺杂和离子液体组成对双电层及其电容的相对贡献。从这个项目中获得的知识有望通过调节石墨烯结构来控制液体和储存电荷的界面组装。这一奖项反映了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。

Non-technical summary With the ever-increasing need for electrical power on demand, next generation energy storage devices (batteries and supercapacitors) must be designed that can support higher energy densities than current technologies. Therefore, new electrolyte and electrode materials must be explored that allow for higher electrolyte packing densities. To improve electrode/electrolyte interfaces, this project, supported by the Solid State and Materials Chemistry program in the Division of Materials Research at NSF, seeks to understand how the structure of ionic liquids and their arrangement at electrode interfaces may be tuned by precisely controlling electrode geometry on the nanoscale. Single-layer graphene, a carbon-based material, just one-atom thick, which can function as a conductive electrode that is highly flexible, is used to created textured electrodes for this study. The research team investigates the influence of the electrode morphology on the organization of the ionic liquid electrolyte and how it impacts charge storage. In addition to exploring these fundamental science questions, this project supports the education and training of undergraduate and graduate students from diverse backgrounds, at the intersection of materials and surface science, contributing to the development of the energy sector work force in the U.S., by training students in cross-cutting research in a coordinated collaborative environment between the labs of the principle investigators at UIUC and TAMU. Technical summaryWith this grant, supported by the Solid State and Materials Chemistry program in the Division of Materials Research at NSF, the principle investigators (Espinosa-Marzal at UIUC and Batteas at TAMU) test the fundamental hypothesis that by controlling surface morphology and substrate-induced charge doping, along with the chemical composition of the ionic liquids, the local packing density of the liquid on graphene can be precisely modulated. This in turn is expected to afford better control over their charge storage properties. To fill the outlined knowledge gap, the team pursues three major lines of research. New methods to prepare graphene surfaces with precisely controlled charge doping and morphology from the atomic to the nanoscale are developed. In addition, the effects of substrate morphology and charge doping on the interfacial structure of ionic liquids and on the characteristics of the electrical double layer are investigated by Atomic Force Microscopy in an electrochemical cell. Furthermore, local and global electrochemical impedance spectroscopy are used to relate the electrical double layer to the differential capacitance of the textured interfaces. These studies allow determining the relative contributions of graphene roughness, charge doping and ionic liquid composition on the electrical double layer and its capacitance. The knowledge gained from this project is expected to enable control of the interfacial assembly of the liquids and stored charge through the modulation of the graphene texture.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.