Abstract The proton exchange membrane (PEM) fuel cell is an ideal automotive power source with great potential, owing to its high efficiency and zero emissions. However, the durability and life-span limit its large-scale application. Complex automotive operating conditions significantly accelerate fuel cell aging, and result in diverse degradation mechanisms that require comprehensive understanding. This review focuses on three harsh conditions of open-circuit/idling, dynamic load, and startup-shutdown. In-situ and ex-situ accelerated stress tests (ASTs) for the three conditions are summarized in terms of methodology, research objectives, and conditions of application. Reversible decay may arise during ASTs and lead to an over-estimation of the aging state, of which the causes and recovery procedures are emphasized. The degradation mechanisms are elaborated systematically according to parameter characteristics, microstructure, and aging reactions. First, increased gas permeation and a high cathode potential during open-circuit/idling combine to intensify generation of free radicals that cause membrane degradation. Pt degradation and migration are also accelerated, characterized by increased Pt particle growth and precipitation in the membrane. The debate regarding the effect of Pt precipitation on membrane degradation is resolved based on a literature review. Second, dynamic load brings about changes in the thermal/humidity state, altered reactant demand, and potential cycling, which lead to mechanical degradation, gas starvation, and Pt particle growth, respectively. To account for the accelerated particle growth, electrochemical Ostwald ripening and increased Pt dissolution are reviewed. Third, an air/hydrogen boundary appears in the anode under startup-shutdown condition and causes carbon corrosion in the local cathode via the reverse current mechanism. The cathode thereby suffers from severe and non-uniform structural damage and even structural collapse, accompanied by Pt agglomeration and detachment. Meanwhile, difficulties in mass transfer arise because of ionomer redistribution, decreased porosity, and carbon surface hydrophilization. In addition, cold start produces severe damage to component structures. This paper seeks to guide further investigation into improved fuel cell durability via mechanism analysis, condition optimization, control strategy development, structural design of the membrane electrode assembly, and component material development.

中文翻译：

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典型汽车工况下质子交换膜燃料电池的降解机理

摘要 质子交换膜（PEM）燃料电池具有高效、零排放等优点，是一种潜力巨大的理想汽车电源。然而，耐用性和寿命限制了其大规模应用。复杂的汽车运行条件会显着加速燃料电池的老化，并导致需要全面了解的各种退化机制。本综述重点关注开路/空转、动态负载和启动-关闭这三种恶劣条件。从方法学、研究目标和应用条件方面总结了这三种条件的原位和异位加速应力测试 (AST)。在 AST 期间可能会出现可逆衰变并导致对老化状态的高估，因此强调了其原因和恢复程序。根据参数特征、微观结构和老化反应系统地阐述了降解机制。首先，在开路/空闲期间增加的气体渗透和高阴极电势结合起来会加剧导致膜降解的自由基的产生。Pt 降解和迁移也会加速，其特征是膜中 Pt 颗粒的生长和沉淀增加。关于 Pt 沉淀对膜降解影响的争论已根据文献综述得到解决。其次，动态负载会导致热/湿度状态的变化、反应物需求的改变和潜在的循环，这分别导致机械降解、气体不足和 Pt 颗粒生长。为了解释加速的粒子生长，综述了电化学 Ostwald 熟化和增加的 Pt 溶解。第三，在启动-关闭条件下，阳极中出现空气/氢边界，并通过反向电流机制在局部阴极中引起碳腐蚀。阴极因此遭受严重且不均匀的结构损坏甚至结构坍塌，伴随着 Pt 的团聚和脱离。同时，由于离聚物重新分布、孔隙率降低和碳表面亲水化，导致传质困难。此外，冷启动会对部件结构造成严重损坏。本文旨在通过机理分析、条件优化、控制策略开发、膜电极组件的结构设计和组件材料开发来指导进一步研究提高燃料电池的耐久性。