Mechanisms of Proton Transport in Ionic Liquids: Grotthuss vs Vehicular

来自田纳西大学的Sokolov和Paddison教授将离子液体的实验和计算研究结合起来，揭示了阐明高效质子传输机制的重要要求。质子是失去单个电子的氢原子，因此带正电。质子运动对各种生物系统的功能（例如，能量产生和神经功能）至关重要，在许多技术应用中也很重要，例如能量转换和存储。离子液体是其组成分子本身带电的物质。例如，中性分子可以从其结构中释放出一个质子（+1电荷），从而使其本身成为一个带负电荷（-1）的离子。离子液体是一类很有前途的能源技术应用物质，因为它们可以促进质子的快速传输（换句话说，它们可以具有高导电性）。教授。Sokolov和Paddison正试图区分质子传输的各种机制。其中，“Grotthuss机制”导致高导电性，因为它是由几个质子同时协同运动产生的。实验鉴定这一机制并了解其相对于不同类型分子结构的发生将大大提高我们设计离子液体应用分子的能力。本提案的总体目标是发展对质子离子液体中控制质子传输的化学和结构方面的基本分子水平的理解。PIs希望通过选择质子受体和质子供体的正确组合，揭示具有极低质子转移能垒的体系。此外，他们还着重于相关质子动力学的分析，以寻找集体grotthsus -like质子转移机制的实验证据。为了实现这些目标，pi采用宽带介电和光散射光谱、中子散射、流变学和核磁共振研究，所有这些都与基于密度泛函理论（DFT）的电子结构计算和从头算分子动力学模拟密切相关。这项工作的广泛影响包括对质子输运机制的预测性理解带来的重大社会效益，以及在高级实验和复杂模拟方面培训学生和博士后的机会。该奖项反映了美国国家科学基金会的法定使命，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。

Professors Sokolov and Paddison from the University of Tennessee combine experimental and computational studies of ionic liquids to unravel important requirements for elucidating highly efficient proton transport mechanisms. Protons are hydrogen atoms that are missing their single electron, and therefore positively charged. Proton motion is vital for the function of various biological systems (for example, energy production and nerve function) and is important in many technological applications, such as energy conversion and storage. Ionic liquids are substances in which the constituent molecules are themselves charged. For example, a neutral molecule can release a proton (+1 electrical charge) from its structure, thus rendering itself a negatively charged (-1) ion. Ionic liquids are a promising class of substances for energy technology applications because they can facilitate very fast transport of protons (in other words they can be highly electrically conductive). Profs. Sokolov and Paddison are seeking to distinguish the various mechanisms of proton transport. One these, the "Grotthuss mechanism" leads to high conductivity because it arises from the cooperative motion of several protons at a time. Experimental identification of this mechanism and understanding its occurrence relative to different kinds of molecular structures would greatly advance our ability to design molecules for ionic liquid applications.The overarching goal of this proposal is to develop a fundamental molecular level understanding of the chemical and structural aspects that control proton transport in protic ionic liquids. The PIs expect to reveal systems with extremely low energy barriers for proton transfer by choosing the right combination of proton acceptors and proton donors. In addition, they focus on analysis of correlated proton dynamics in search for experimental evidences of the collective Grotthuss-like proton transfer mechanism. To achieve these goals the PIs employ broadband dielectric and light scattering spectroscopies, neutron scattering, rheology, and NMR studies, all in tight connection with density function theory (DFT) based electronic structure calculations and ab-initio molecular dynamics simulations. The broader impact of this work includes significant societal benefits from a predictive understanding of proton transport mechanisms, as well as opportunity for training students and postdoctoral associates in advanced experiments and complex simulations.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.