Fundamental Study of the Degradation Mechanisms of Polymer Electrolyte Membranes for PEM Fuel Cells

CBET-0829082黄膜耐久性是聚合物电解质膜(PEM)燃料电池商业化的重要技术障碍，PEM燃料电池是一种高效、清洁的能源转换设备，可以从氢气中产生电能。燃料电池膜的针孔形成和机械脆化导致了常见的猝死现象，限制了PEM燃料电池装置的使用寿命。认为局部膜衰变是导致燃料电池膜弱化和破裂的主要原因。这项建议的目的是通过新的原位诊断方法、数值模拟和尸检分析来探索局部或不均匀膜衰变现象的基本机制。智力优势：初步证据表明，根据操作历史的不同，膜衰变可以以不同的方式发生：均匀的或局部的。假设局部膜衰减是一系列事件的结果，这些事件可能包括局部水淹、局部燃料匮乏、膜电位分布扰动、碳腐蚀和铂溶解以及膜的不均匀衰减。衰变现象的局部化被认为是由于事件的自我放大(相对于自熄灭)的性质，因为它们倾向于创造条件，稳定和加强局部膜衰变过程。为了证明这一假设，提出了新的原位诊断方法，以帮助更详细地揭示局部膜衰变过程。其中包括共聚焦显微拉曼光谱和高分辨率中子成像。这两种技术都将被实施，以获得运行PEM燃料电池时膜降解状态的原位地图。该地图的空间(像素)分辨率预计为1x1x1微米。测量到的局部密集变量将被输入到预测膜电位分布的模拟模型中，以及对碳腐蚀、铂溶解和膜变薄敏感的区域。这些预测将通过尸检分析进一步得到证实。如果成功，所提出的方法将产生燃料电池运行中膜降解过程的第一张原位逐点图像。与传统的诊断技术相比，所提出的原位诊断方法具有显著的优势，可用于研究与离聚体膜相关的各种新出现的和具有挑战性的问题。更深入地了解膜的不均匀降解机理将为设计更好的材料、更好的电池/堆叠结构以及创新的膜降解缓解策略提供方向，以提高PEM燃料电池的使用寿命。更广泛的影响：拟议的计划将把大学教授、研究生和本科生聚集在一起进行令人兴奋的研究工作，这有可能加速氢和燃料电池技术的商业化。作为教育工作的一部分，将招募女性和少数族裔学生作为暑期实习生参与该项目。PI和学生将帮助创建燃料电池丰富的科学课程单元，并将其提供给K-12教师。这些课程的采用和传播有望激发和激励大量K-12学生在能源促进可持续发展的广泛领域进行研究。

CBET-0829082HuangMembrane durability is a significant technical barrier for the commercialization of polymer electrolyte membrane (PEM) fuel cells, which are efficient and clean energy conversion devices that can produce electricity from hydrogen. The pinhole formation and mechanical embrittlement of fuel cell membranes lead to the frequently observed "sudden death" behavior, which limits the service life of PEM fuel cell devices. It is believed that the localized membrane decay is largely responsible for the weakening and the breach of the fuel cell membrane. The objective of this proposal is to explore the fundamental mechanisms of the localized or inhomogeneous membrane decay phenomena through novel in situ diagnostic methods, numerical modeling, and post-mortem analysis. Intellectual Merit: Preliminary evidence has shown that, depending on the operation history, the membrane decay can occur in different modes: uniform or localized. It is hypothesized that the localized membrane decay is a result of a sequence of events, which may include local flooding, local fuel starvation, perturbated membrane potential distribution, carbon corrosion and Pt dissolution, and inhomogeneous membrane decay. The localization of the decay phenomena is thought to be due to the self-amplifying (as against self-extinguishing) nature of the events in that they tend to create conditions that stabilize and reinforce the local membrane decay processes. To prove this hypothesis, novel in situ diagnostic methods are proposed to help reveal the local membrane decay processes in great details. These include confocal micro-Raman spectroscopy and high-resolution neutron imaging. Both techniques will be implemented to obtain in situ maps of the membrane degradation state in running PEM fuel cells. The map is expected to have a spatial (pixel) resolution on the order of 1 by 1 by 1 micron. The measured local intensive variables will be fed into simulation models that predict membrane potential distribution as well as regions that are susceptable to carbon corrosion, Pt dissolution and membrane thinning. These predictions will be further validated by post-mortem analysis. If succesful, the proposed method will result in the first in situ point-wise pictures of the membrane degradation processes in running fuel cells. The proposed in situ diagnostic methods offer significant advantages over traditional diagnostic techniques, and can be used to study various emerging and challenging problems that are related to ionomer membranes. The greater understanding of the mechanisms of the inhomogeneous membane degradation will suggest directions for engineering better materials, better cell/stack configuration, and innovative membrane degradation mitigation strategies to improve the service life of PEM fuel cells.Broader Impact: The proposed program will bring university professors, graduate and undergraduate students together in an exciting research effort, which has the potential to accelerate the commercialization of hydrogen and fuel cell technologies. As part of the education effort, female and minority students will be recruited to work on the project as summer interns. The PI and the students will help create and provide fuel cell enriched science curricula units to K-12 teachers. The adoption and dissemination of these curricula will hopefully intrigue and inspire a large number of K-12 students to pursue research in the broad area of energy for sustainability.