The role of electrolyte/cathode interfacial structure on performance of proton exchange membrane fuel cells

质子交换膜燃料电池是一种替代能源转换装置，可以有效地将化学能转化为电能，在交通运输中用作动力。这些装置的低效与特定化学过程的能量学有关，并限制了它们的性能。目前最先进的设备不能同时满足效率、功率输出、成本和耐用性目标。大部分性能损失被分配到氧还原阴极的过程中，其中功率/效率损失、昂贵的铂催化剂的非最佳利用以及对反应物氧气流动相对湿度的敏感性对实际设备的开发构成了挑战。这些损失在一定程度上可以归因于铂催化剂颗粒-聚合物电解质界面的设计不完善。然而，目前改进该接口设计的尝试受到对其在指示设备性能方面的作用缺乏基本了解的限制。质子交换膜燃料电池(PEMFC)中膜/阴极电催化界面的研究目标是：(1)使用分子动力学和量子力学方法对膜/阴极电催化界面进行适当的建模；(2)描述湿度和电化学势对该界面结构和氧还原反应动力学的影响；(3)估计由于非理想的电解液/电极界面结构而造成的PEMFC性能损失。提出了一种多尺度、集成的分子模拟方法来研究电极/电解液界面结构对氧还原反应速率的影响。分子动力学(MD)将被用来探测这种界面的结构作为电极电位和水合的函数。量子力学(QM)方法将被用来量化基本氧还原反应动力学对该界面结构的依赖关系。在应用MD和QM方法研究电化学界面方面将取得新的进展。总而言之，这些方法将建立反应速度作为水化和电极电位的函数，这与PEMFC的效率和功率输出直接相关。因此，该接口的结构可以与PEMFC的性能损失联系在一起，从而提供改进器件设计所需的基本结构-性能关系。更广泛的影响：拟议的工作将：(1)通过探测这些组件之间的界面，整合目前分别专注于膜材料和电极设计的能量转换装置的分子建模方面的研究工作；(2)通过培训研究生将分子建模技术应用于能量转换过程的研究，加强正在进行的研究；以及(3)通过开发该领域的高级课程，将这一培训扩展到具有前瞻性的研究小组之外；让代表性不足群体的本科生在大学生涯早期参与使用分子建模技术的研究。将开发一门强调能量应用的分子建模高级课程。为本课程开发的模块将向技术社区提供和宣传。研究生研究人员将接受高级技术培训，并特别强调研究成果的有效交流。此外，拟议研究的组成部分将通过宾夕法尼亚州立大学现有的计划作为研究项目提供，以招募和激励女性和少数族裔本科生利用计算机技术从事研究工作。

Proton exchange membrane fuel cells are an alternative energy conversion device that may efficiently convert chemical energy to electrical energy for use as motive power in transportation applications. Inefficiencies in these devices are associated with the energetics of specific chemical processes and constrain their performance. The current state-of-the-art devices can not simultaneously meet efficiency, power output, cost, and durability targets. A majority of the performance losses are allocated to processes at the oxygen reduction cathode, where power/efficiency losses, non-optimum utilization of expensive platinum catalyst, and sensitivity to the reactant oxygen stream relative humidity challenge the development of practical devices. These losses can, in part, be attributed to imperfect design of the Pt catalyst particle-polymer electrolyte interface. However, current attempts to improve the design of this interface are limited by a lack of fundamental understanding of its role in dictating device performance. The complexity inherent in this interface and the need to characterize it under operating conditions limit the ability of experimental techniques to link interfacial structure to PEMFC performance.Intellectual Merit: The research objectives of the proposed work are to (1) appropriately model the membrane/cathode electrocatalytic interface in a proton exchange membrane fuel cell (PEMFC) using both molecular dynamics and quantum-mechanical methods; (2) to describe the influence of humidity and electrochemical potential on the structure of this interface and on oxygen reduction reaction kinetics; and (3) to estimate the losses in PEMFC performance due to a non-ideal electrolyte/electrode interfacial structure. A propose multi-scaled, integrated molecular modeling approach to understand the influence of electrode/electrolyte interfacial structure on oxygen reduction reaction rates is proposed. Molecular dynamics (MD) will be used to probe the structure of this interface as a function of electrode potential and hydration. Quantum-mechanical (QM) methods will be used to quantify the dependence of the elementary oxygen reduction reaction kinetics on this interfacial structure. Method advances in both the application of MD and QM methods to the electrochemical interface will be developed. Collectively, these methods will establish the rate of reaction as a function of hydration and electrode potential, which is directly linked to the PEMFC efficiency and power output. Therefore, the structure of this interface can be linked to PEMFC performance losses thus providing the fundamental structure-performance relationships needed to improve device design. Broader Impact: The proposed work will (1) integrate research efforts in the molecular modeling of energy conversion devices currently concentrating separately on membrane materials and electrode design by probing the interface between these components; (2) enhance ongoing research by training graduate students in the application of molecular modeling techniques to the study of energy conversion processes; and (3) to extend this training beyond the perspective research groups through the development of an advanced course in this area; to involve undergraduates from under-represented groups in research using molecular modeling techniques early in their collegiate careers . An advanced course in molecular modeling emphasizing energy applications will be developed. The modules developed for this course will be made available and publicized to the technical community. Graduate student researchers will receive advanced technical training with additional emphasis on the effective communication of research results. Additionally, components of the proposed study will be offered as research projects through established Penn State programs to recruit and motivate women and minority undergraduate students towards research careers utilizing computational techniques.