Molecular modeling of interfacial structure and dynamics in proton conductors for fuel cells

这个程序在理论和分子模拟中探索质子沿水合界面的传输，质子结合表面基团密集排列。这些现象在许多领域都是至关重要的，包括生物能量学中质子沿着细胞膜运动以及氢燃料电池中的能量转换。我们的主要兴趣在于后一个领域。燃料电池是一种高效、环保的电化学能量转换器。它们正在深入研究，以应用于车辆运输和许多需要便携式电源的设备。燃料电池研究的重点是开发具有高质子导电性、高稳定性、良好保水性和低成本的先进聚合物电解质膜。我们的主要目标是促进对质子导电介质中结构-性质关系的基本理解。因此，我们接近建立合理设计先进燃料电池膜的理论框架的长期目标。对于质子输运机制的研究，我们采用低水合的规则二维带电表面基团阵列作为模型系统。我们利用完整的从头算分子动力学计算来揭示这些模型结构中远程质子输运的途径。为了克服分子运动和质子转移事件发生的时间尺度差异，我们采用了跃迁路径采样技术。计算了质子输运的活化能和速率。我们的计算结果提供了质子迁移率与控制界面阵列结构参数（如聚合物的化学组成、表面基团的长度和密度）之间的关系。该项目为学生提供了极好的培训机会。他们学习如何在理论物理和化学中使用相关工具，并将其应用于燃料电池研究和电化学材料科学中的首要挑战。

This program in theory and molecular modeling explores proton transport along hydrated interfaces with dense packing of proton binding surface groups. These phenomenona are vital for a wide range of areas, including proton motion along cellular membranes in bioenergetics as well as energy conversion in hydrogen fuel cells. Our main interest lies in the latter realm.    Fuel cells are highly efficient and environmentally benign electrochemical energy converters. They are under intensive research for applications in vehicular transportation and many devices requiring portable power. Tremendous efforts in fuel cell research focus on the development of advanced polymer electrolyte membranes with high proton conductivities, high stability, good water retention, and low cost.    Our main objective is to contribute to the fundamental understanding of structure-property relationships in proton conducting media. Thereby, we approach the long-standing goal of establishing a theoretical framework for the rational design of advanced fuel cell membranes. For our studies of proton transport mechanisms we employ a lowly hydrated regular 2D array of charged surface groups as a model system. We utilize full ab-initio molecular dynamics calculations to unravel pathways of long-range proton transport in these model structures. In order to overcome the disparity of time scales between molecular motions and the occurence of proton transfer events we employ transition path sampling techniques. Activation energies and rates of proton transport are calculated. Results of our calculations furnish relations between  proton mobility and controlled structural parameters of the interfacial array (e.g. chemical composition of the polymer, length and density of surface groups).         This program provides excellent training possibilities for students. They learn how to use pertinent tools in theoretical physics and chemistry and apply them to foremost challenges in fuel cell research and electrochemical materials science.