The study investigates the freezing behavior of supercooled water in gas diffusion layers (GDLs) of polymer electrolyte fuel cells (PEFCs). Using an innovative advanced differential scanning calorimetry (advanced DSC) technique, we analyze phase transitions within GDLs at a single-cell scale, excluding impacts of catalyst layers and membranes. This method overcomes the limitations of traditional DSC, allowing variable water saturation and distribution. We find that freezing-thawing and drying-saturating cycles contribute to noticeable variations in the freezing temperature () of supercooled water, ranging from −6 °C to −15 °C, attributed to the heterogeneous surface of GDL and water redistribution. Repeated drying-saturating cycles remove nucleation seeds, lowering the freezing point of water − a "cleaning effect." The freezing probability reduces at lower saturation levels, influenced by waterproof treatment uniformity on GDLs. Residual ice can be detrimental to the cold-start capability of PEFCs, as it promotes freezing of supercooled water around −1 °C. Our findings enhance understanding of water behavior in GDLs and its impact on PEFC cold-start performance. Applying this technique to other cell components, such as the catalyst layer, could further elucidate water freezing dynamics in PEFCs and guide the innovation of more reliable cell components for PEFC applications in broader climates.

中文翻译：

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利用先进的原位差示扫描量热法定量观察气体扩散层中的水相变

该研究调查了聚合物电解质燃料电池（PEFC）气体扩散层（GDL）中过冷水的冻结行为。使用创新的先进差示扫描量热法（先进 DSC）技术，我们在单细胞规模上分析 GDL 内的相变，排除催化剂层和膜的影响。该方法克服了传统 DSC 的局限性，允许可变的水饱和度和分布。我们发现，冷冻-解冻和干燥-饱和循环导致过冷水的冷冻温度 () 发生显着变化，范围从 -6 °C 到 -15 °C，归因于 GDL 的异质表面和水的重新分布。重复的干燥-饱和循环可以去除成核种子，降低水的冰点——一种“清洁效果”。受 GDL 防水处理均匀性的影响，饱和度较低时结冰概率会降低。残留的冰可能不利于 PEFC 的冷启动能力，因为它会促进 -1 °C 左右的过冷水结冰。我们的研究结果加深了对 GDL 中水行为及其对 PEFC 冷启动性能影响的理解。将该技术应用于催化剂层等其他电池组件，可以进一步阐明 PEFC 中的水结冰动力学，并指导在更广泛的气候条件下为 PEFC 应用提供更可靠的电池组件的创新。