Catalyst degradation in PEM fuel cells: from physical understanding to mitigation

我们提出了一项为期三年的研究合作，旨在了解和缓解汽车用聚合物电解质燃料电池(PEFC)中的催化剂降解机理。主要模块侧重于开发一套一致的建模工具。建模将与实验和测试工作密切协调，由学术界和工业界的合作者进行。车用PEFC在其生命周期中会经历数千次正常运行事件，如启动/关闭、加速、稳定爬升或怠速。在此生命周期中，需要保持严格的性能级别。相应地，行业和政府对退化设定了严格的限制。因此，研究活动集中在解开铂基电催化剂系统的电催化活性、稳定性和成本的相互关联的方面。计划中的协作和跨学科研究计划的理论部分将产生对催化剂降解现象的一致理解。这项研究将跨越相关的规模层次，包括对扩展表面催化剂的原子研究，对分布在平面衬底表面的催化剂纳米颗粒模型系统的介观研究，以及对PEFC中全功能阴极催化层的宏观研究。模型将通过与非现场实验和单个运行的燃料电池的现场测试进行系统比较来证实和逐步完善。探讨了不同的反应条件和典型的加速应力试验电压变化方案对催化剂质量损失和再分布的影响。预期的结果包括对燃料电池如何降解的基本了解，对材料参数和局部反应条件如何影响耐久性的诊断了解，以及对运营系统管理可以做些什么来缓解压力的实际了解。这一理解将导致一系列实用的建议，用于催化剂层的结构设计和操作条件的微调，以延长PEFC中铂基催化剂的寿命。

We propose a three-year research collaboration designed to understand and mitigate catalyst degradation mechanisms in polymer electrolyte fuel cells (PEFC) for automotive applications. The main modules focus on the development of a consistent suite of modeling tools. Modeling will be conducted in close coordination with experimental and testing work, conducted by collaborators in academia and industry. An automotive PEFC, during its lifetime, is subjected to thousands of normal operational events such as start-up/shut-down, acceleration, steady climbs, or idling. Stringent levels of performance need to be maintained over this lifetime. Correspondingly, industry and governments have set strict limits on degradation. Therefore, activities in research focus on unraveling interrelated aspects of electrocatalytic activity, stability and cost of Platinum-based electrocatalyst systems. Theoretical portions of the planned collaborative and interdisciplinary research program will produce a consistent understanding of catalyst degradation phenomena. The research will span the relevant hierarchy of scales, encompassing atomistic studies on extended surface catalysts, mesoscopic studies on model systems of catalyst nanoparticles distributed at plain substrate surfaces, and macroscopic studies on fully functional cathode catalyst layers in PEFC. Models will be corroborated and successively refined by systematic comparison with both ex situ experiments and in situ tests on single operational fuel cells. The impact of varying reaction conditions and typical voltage variation protocols of accelerated stress tests on catalyst mass loss and redistribution will be explored. The anticipated outcomes include fundamental understanding of how fuel cells degrade, diagnostic understanding of how materials parameters and local reaction conditions affect durability, and practical understanding of what operational system management can do to mitigate stressors. This understanding will lead to a list of practical recommendations for structural design of catalyst layers and fine-tuning of operating conditions in order to extend the lifetime of Pt-based catalysts in PEFC.