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

薄膜耐久性是聚合物电解质膜（PEM）燃料电池商业化的一个重要技术障碍，PEM燃料电池是一种高效清洁的能源转换装置，可以从氢气中产生电力。 燃料电池膜的针孔形成和机械脆化导致经常观察到的“突然死亡”行为，这限制了PEM燃料电池装置的使用寿命。 据信，局部膜衰减在很大程度上是导致燃料电池膜弱化和破裂的原因。 该提案的目的是通过新型原位诊断方法、数值建模和事后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，膜衰减可以以不同的模式发生：均匀或局部。 据推测，局部膜衰减是一系列事件的结果，这可能包括局部洪水，局部燃料饥饿，扰动膜电位分布，碳腐蚀和铂溶解，和不均匀的膜衰减。 衰变现象的局部化被认为是由于事件的自放大（相对于自熄灭）性质，因为它们倾向于创造稳定和加强局部膜衰变过程的条件。 为了证明这一假设，提出了新的原位诊断方法，以帮助揭示当地的膜衰变过程的细节。 这些包括共焦显微拉曼光谱和高分辨率中子成像。 这两种技术将被实施，以获得在运行PEM燃料电池的膜降解状态的原位地图。 该地图预期具有1 × 1 × 1微米量级的空间（像素）分辨率。 测得的局部强度变量将被送入模拟模型，预测膜电位分布以及易受碳腐蚀、Pt溶解和膜变薄影响的区域。 这些预测将通过尸检分析得到进一步验证。 如果成功的话，所提出的方法将导致在运行的燃料电池中的膜降解过程的第一个在原位逐点的图片。 提出的原位诊断方法提供了显着的优势，传统的诊断技术，并可用于研究各种新兴的和具有挑战性的问题，与离聚物膜。 对非均匀膜降解机制的更深入理解将为设计更好的材料、更好的电池/电池堆配置和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。拟议的计划将使大学教授，研究生和本科生在一个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，将招募女性和少数民族学生作为暑期实习生参与该项目。 PI和学生将帮助创建和提供燃料电池丰富的科学课程单元，以K-12教师。 这些课程的采用和传播将有望激发和激励大量的K-12学生在能源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.