Abstract In this review, “cold start” is defined as the startup of proton exchange membrane (PEM) fuel cells from subfreezing temperatures. Problems occurring during the cold start pose some of the remaining barriers to commercial applications of PEM fuel cells in transportation, stationary, auxiliary and portable systems. Fundamental studies of transport phenomena are critical to a better understanding of the mechanisms of cold start and offer ultimate solutions to resolving cold-start issues. In this review, experimental studies are discussed, focusing on output performance degradation, water and ice visualization, and component damages during a cold start. Analytical, numerical, and microscopic models and their results are also discussed. One of the emphases is on transport phenomena relevant to cold starts, including supercooling, phase change and transport of water in the membrane, catalyst layer, microporous layer, and gas diffusion layer. Another emphasis is placed on the strategies utilized to optimize cold-start processes for improved performance. The strategies include material designs of the components, cell/stack structures, and startup mode/load controls. It is shown that all of the effective strategies to mitigating cold-start problems derive from a basic understanding of the transport mechanisms during a cold start. It is also suggested that future models for this problem should place a great deal of attention in supercooling phenomena and water phase-change and transport in multilayer porous media. Lastly, more advanced experimental methods, such as real-time water/ice visualization and cryogenic microscopy, are needed to validate emerging theories and models.

中文翻译：

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质子交换膜燃料电池冷启动

摘要 在这篇综述中，“冷启动”被定义为质子交换膜 (PEM) 燃料电池从低于冰点的温度启动。冷启动期间出现的问题对 PEM 燃料电池在运输、固定、辅助和便携式系统中的商业应用构成了一些剩余的障碍。传输现象的基础研究对于更好地理解冷启动机制并为解决冷启动问题提供最终解决方案至关重要。在这篇综述中，讨论了实验研究，重点是输出性能下降、水和冰的可视化以及冷启动期间的部件损坏。还讨论了分析、数值和微观模型及其结果。重点之一是与冷启动相关的传输现象，包括过冷、水在膜、催化剂层、微孔层和气体扩散层中的相变和传输。另一个重点是用于优化冷启动过程以提高性能的策略。这些策略包括组件的材料设计、电池/堆栈结构和启动模式/负载控制。结果表明，所有缓解冷启动问题的有效策略都源于对冷启动过程中传输机制的基本了解。还建议该问题的未来模型应高度关注多层多孔介质中的过冷现象和水相变和输运。最后，需要更先进的实验方法，如实时水/冰可视化和低温显微镜，来验证新兴的理论和模型。