Molecular Physics of the Electrical Double Layers in Ionic Liquids

离子液体中双电层的分子物理

• 批准号: 0967175
• 负责人: Rui Qiao
• 金额: $ 17.84万
• 依托单位: Clemson University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-07-01 至 2014-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0967175&HistoricalAwards=false
• 关键词: Molecular; Physics; Electrical; Double; Layers

0967175QiaoIonic liquids are a new class of electrolytes with many potentially high impact properties such as wide electrochemical windows, low vapor pressure, and excellent thermal stability. These properties offer distinct advantages in electrochemical applications such as solar cells and supercapacitors. In these potential applications, the electrical double layers (EDLs) at the interfaces of electrodes and ionic liquids play a critical role in determining the system performance. However, the knowledge on these EDLs is very limited: many fundamental issues such as the capacitance potential correlation and the capacitance of EDLs in ultrasmall nanopores are poorly understood at present. Such a limited understanding renders the design and optimization of electro-chemical systems using ionic liquids as electrolyte difficult, and thus prevents the potential of ionic liquids from being fully exploited. Therefore, it is critical to improve our understanding of the EDLs in ionic liquids. The objective of this research is to investigate the electrical double layers (EDLs) in ionic liquids using molecular dynamics simulations. Specifically, the PI will first study the EDLs at the interfaces of ionic liquids and planar electrodes to delineate how their structure and capacitance are affectedby the electrical/physicochemical properties of electrodes and ions. The EDLs in ionic liquids-filled sub-nanometer pores will then be studied to elucidate the synergistic effects of nano-confinement and surface curvature on the structure and capacitance of EDLs in these pores.Intellectual Merit: In the study of planar EDLs, a new picture for the EDLs in ionic liquids, i.e., the Ion-ion and ion-electrode correlations play a key role in determining the EDL structure, is proposed. This picture represents a paradigm shift from the prevalent EDL models, and is supported by compelling preliminary data. Guided by this new idea, the PI?fs simulation design and data analysis differ distinctly from those in prior research and are expected to lead to new insights into the dependence of EDL structure on the nature of ions and on the polarization/chemistry of electrodes. With this, the PI will elucidate the mechanism of the diverse capacitance?]potential relations and surprising ion specificity of EDL observed in previous experiments, which defy existing EDL models. In the study of EDLs in sub-nanometer pores, by doing simulations in pores with precisely defined geometry and by simultaneously computing the microstructure and capacitance of the EDLs, the PI's group will, for the first time, self-consistently test the prior hypotheses on effects of confinement and surface curvature on EDL capacitance in sub-nanometer pores, and elucidate the underlying mechanisms of the test result. Together, these researches will greatly advance the fundamental understanding of the EDLs in ionic liquids and make a firm step towards building the knowledge base for the rational design of electrochemical systems using ionic liquids as working electrolytes.Broader Impacts: The project will be tied intimately with the educational activities at Clemson University. Students participating in this project will be exposed to diverse fields such as physical chemistry, atomistic modeling and computational methods. Undergraduate students will be involved in the research through the Honors Research Program in the PI's home department. Various resources, e.g., the minority recruitment programs at Clemson University, will be utilized to recruit students from underrepresented groups to participate in this project. Research results will be developed into posters/movies to introduce electrical energy storage to K-12 students. Research will be disseminated through journal publications and presentations in professional conferences. A website centering on the fundamental physics of the EDLs in ionic liquids and their role in electrochemical systems will be developed and maintained. The website will be advertised to the target audience via formal and informal channels.

0967175Qiao离子液体是一类新型电解质，具有许多潜在的高冲击性能，例如宽电化学窗口、低蒸气压和出色的热稳定性。这些特性在太阳能电池和超级电容器等电化学应用中提供了明显的优势。 在这些潜在的应用中，电极和离子液体界面处的双电层（EDL）在确定系统性能方面发挥着关键作用。然而，对这些 EDL 的了解非常有限：目前对超小纳米孔中 EDL 的电容电位相关性和电容等许多基本问题了解甚少。这种有限的认识使得使用离子液体作为电解质的电化学系统的设计和优化变得困难，从而阻碍了离子液体的潜力得到充分开发。因此，提高我们对离子液体中 EDL 的理解至关重要。 本研究的目的是利用分子动力学模拟研究离子液体中的双电层 (EDL)。具体来说，PI 将首先研究离子液体和平面电极界面处的 EDL，以描述电极和离子的电/物理化学性质如何影响它们的结构和电容。然后将研究离子液体填充的亚纳米孔隙中的 EDL，以阐明纳米约束和表面曲率对这些孔隙中 EDL 的结构和电容的协同效应。 智力优点：在平面 EDL 的研究中，离子液体中 EDL 的新图像，即离子-离子和离子-电极相关性发挥了重要作用。 提出了在确定 EDL 结构中的关键作用。这张图代表了流行的 EDL 模型的范式转变，并得到了令人信服的初步数据的支持。在这一新想法的指导下，PI?fs 模拟设计和数据分析与之前的研究明显不同，预计将带来关于 EDL 结构对离子性质和电极极化/化学性质的依赖性的新见解。由此，PI 将阐明先前实验中观察到的不同电容电位关系和令人惊讶的 EDL 离子特异性的机制，这违背了现有的 EDL 模型。在亚纳米孔隙中EDL的研究中，通过在具有精确定义的几何形状的孔隙中进行模拟，并同时计算EDL的微观结构和电容，PI团队将首次自洽地检验先前关于亚纳米孔隙中约束和表面曲率对EDL电容影响的假设，并阐明其潜在机制。 测试结果。总之，这些研究将极大地促进对离子液体中 EDL 的基本理解，并朝着建立使用离子液体作为工作电解质的电化学系统的合理设计知识库迈出坚实的一步。 更广泛的影响：该项目将与克莱姆森大学的教育活动密切相关。参与该项目的学生将接触物理化学、原子建模和计算方法等不同领域。本科生将通过 PI 所在部门的荣誉研究计划参与研究。 将利用各种资源，例如克莱姆森大学的少数族裔招聘计划，招募代表性不足群体的学生参与该项目。研究成果将被制作成海报/电影，向 K-12 学生介绍电能存储。研究成果将通过期刊出版物和专业会议上的演讲进行传播。将开发和维护一个以离子液体中 EDL 的基础物理及其在电化学系统中的作用为中心的网站。该网站将通过正式和非正式渠道向目标受众进行广告宣传。