Applying computational chemistry to the study of proton exchange membranes/ Étude par modélisation moléculaire de membranes échangeuses de protons

聚合物电解质膜燃料电池（PEMFC）是目前正在开发的用于汽车应用的主要系统。然而，要使燃料电池在经济上与其他替代方案（如高性能柴油或混合动力汽车）竞争，还需要进行一些改进。在这个提议中，一个层次的一系列计算化学方法被用于解决质子交换膜（PEM）的高温低湿性能问题。该程序旨在通过来自不同计算化学方法的数据与实验结果之间的密切联系来捕捉分子行为的洞察力。因此，从分子水平上理解控制PEM性能的物理机制将有助于推进其发展，从而提高燃料电池的最终效率。该初级阶段的目的是通过比较计算的中尺度形态和实验确定的结构，阐明控制PEMFC所用膜的实际基准聚合物Nafion®的相分离和自组织规模的因素。这些特征将为初步评价所建议方法的准确性提供基础。下一个重点是将在Nafion®工作期间开发的方法应用于GM目前正在开发的新合成的嵌段共聚物PEMs。这些嵌段共聚物的拟议计算旨在补充并为GM现有的和计划中的这些膜的实验程序提供背景。对改进膜合成的指导也期望从这样的比较。最终目标是开发一种完全成熟的方法，可以根据化学成分、组成块的长度和多分散性来预测随机和嵌段共聚离聚体结构相稳定性的变化。在计算理论和实验之间的迭代过程中利用实验结果被视为取得实质性进展的重要组成部分。这种交流是舍布鲁克大学和通用汽车加拿大有限公司目前合作的核心。

Polymer electrolyte membrane fuel cells (PEMFC's) are the primary system being developed for use in automotive applications. Nevertheless, some improvements have to be achieved to make fuel cells economically competitive with other alternative solutions, such as high performance diesel, or hybrid vehicles. In this proposal, a hierarchical series of computational chemistry methods is used to solve the high-temperature low-humidity performance problems of proton exchange membranes (PEM). The procedure is intended to capture the insight of molecular behaviour through the intimately link between data stemming from the different computation chemistry methods, and the experimental results. A molecular level understanding of the physical mechanisms controlling PEM performance should thus help advance their development and therefore improve the final efficiency of fuel cells. The purpose of this primary phase is to clarify the factors governing the scale of phase segregation and self-organization in Nafion®, the actual benchmark polymer for membranes used in PEMFC, by comparing the calculated mesoscale morphology to its experimentally determined structure. These features will provide the basis for an initial evaluation of the accuracy of the proposed methodology.  The next focus is to apply the methods developed during the Nafion® work to newly synthesized block copolymer PEMs currently being developed by GM.  The proposed calculations on these block copolymers are intended to complement and provide context to GM's existing and planned experimental program on these membranes. Guidance on improving membrane synthesis is also anticipated from such comparisons.  The final goal is a fully developed methodology that can predict changes in the stability of the structural phases of both random and block copolymer ionomers based on the chemical composition, length of the component blocks, and polydispersity. Leveraging of experimental results in an iterative process between computational theory and experiment is viewed as essential component for making substantial progress. This interchange is central to the current collaboration between Université de Sherbrooke and GM Canada Limited.