Using SESANS to discover the PEM fuel cell catalyst layer's structure & porosity

The anode and cathode catalyst layer of a PEM fuel cell should possess a porous structure, which influences the mass transport of the gasses towards the surface of the platinum catalyst. Furthermore, water is present in the catalyst layers, where an inappropriate structure can cause flooding within the catalyst layer. The mass transport of the gasses and flooding of the catalyst layer influence the performance and durability of the PEM fuel cell.

During our previous measurement at ISIS, we were able to do a SESANS measurement on a complete single fuel cell. The results clearly indicate that features can be measured with the SESANS on a higher length scale compared to the standard SANS. Also in literature, the SESANS has already been proven to be a good technique to analyze the bulk structures in polymer-carbon nanocomposites. For our SESANS measurement on the single fuel cell, the membrane can highly possible be excluded because no features are expected on the larger scale. However, the catalyst layers with different porosities are expected to play a role on the length scale measured by the SESANS. Therefore, it would be desired to evaluate further if the SESANS would be a novel measurement method to extract information of the PEM fuel cell catalyst layer’s structure.

质子交换膜（PEM）燃料电池的阳极与阴极催化层应具备多孔结构，该结构会影响气体向铂催化剂表面的传质过程。此外，催化层中存在水分，若结构不当则会引发催化层内的水淹现象。气体传质与催化层水淹会影响质子交换膜（PEM）燃料电池的性能与耐久性。

此前我们在散裂中子源（ISIS）开展实验时，已对完整的单燃料电池完成了自旋回声小角中子散射（SESANS）测试。测试结果清晰表明，相较于标准小角中子散射（SANS），自旋回声小角中子散射（SESANS）可在更大的长度尺度下观测到特征结构。此外，已有文献证实自旋回声小角中子散射（SESANS）是一种用于分析聚合物-碳纳米复合材料本体结构的优质技术。针对本次单燃料电池的自旋回声小角中子散射（SESANS）测试，由于大尺度下无预期特征，膜结构大概率可以被排除在分析范围之外。而不同孔隙率的催化层则被认为会对自旋回声小角中子散射（SESANS）所测得的长度尺度产生影响。因此，我们需要进一步评估自旋回声小角中子散射（SESANS）是否可作为一种新型测试方法，用以提取质子交换膜（PEM）燃料电池催化层的结构信息。