NSERC-DFG SUSTAIN: In-operando Visualization of catalyst ion transport in PEM fuel cells and electrolyzers

为了以环境可持续的方式满足日益增长的能源需求，德国和加拿大已经认识到氢气是能源部门脱碳的最有前途的途径之一。聚合物电解质膜（PEM）燃料电池和PEM电解槽是这种氢经济的关键技术。为了大规模采用这些技术，必须提高长期稳定运行和降低成本。控制持久操作的两个薄弱环节是催化剂浸出和PEM降解。催化剂离子的降解和浸出对催化剂的电化学活性区域产生负面影响，降低总反应速率并导致性能损失。更具体地，催化剂金属离子从催化剂层进入PEM的移动以及它们的再沉积被认为是至关重要的，但描述得很差。这种现象强烈地受到PEM中的水化分布的影响。此外，在燃料电池和电解槽中使用对环境有害的氟碳基膜目前受到质疑，并且新型烃基膜有望取代它们。在这个项目中，我们的目标是在不同的长度尺度上的聚电解质膜的水和离子传输的动力学特性。为了深入了解控制燃料电池和电解槽耐久性的因素，该项目将新型实验技术（如操作中可视化和非原位和死后膜表征）与数值模拟相结合。微流体模型系统将被用来研究在微观尺度上的传输现象。一个更大的细胞，包括相同的膜和电极材料作为经典的实验室规模的设置，将提供洞察水化水平的影响，并作为微流体和台式规模之间的桥梁。在台式电池中，将测试常规氟碳化合物和新型烃PEM以比较电化学性能、PEM水合以及催化剂和膜降解。此外，模拟将有助于微观尺度和宏观尺度结果的比较和解释。对于在微流控单元中的水和离子传输的原位表征，将主要使用基于荧光的成像方法。对于台式规模，将采用更传统的膜和电池表征方法，包括膜的吸水率和质子电导率测量，以及膜电极组件的电子显微镜和元素分析。通过了解微观和宏观尺度上的传输过程的基本原理，我们提出的新实验将直接有助于新材料的设计和开发，以及减轻PEM燃料电池和电解槽退化的操作策略的确定。

To meet increasing energy demands in an environmentally sustainable manner, Germany and Canada have recognized hydrogen as one of the most promising pathways for decarbonizing the energy sector. Polymer-electrolyte membrane (PEM) fuel cells and PEM electrolyzers are key technologies in this hydrogen economy. For the large-scale adoption of these technologies, an enhancement in stable long-term operation and a reduction in cost is necessary. The two weak links controlling durable operations are catalyst leaching and PEM degradation. Degradation and leaching of catalyst ions negatively impact the electrochemically active area of the catalyst, reducing the overall reaction rate and resulting in performance loss. More specifically, the movement of catalyst metal ions from the catalyst layer into the PEM, as well as their re-deposition, is understood to be of critical importance but is poorly described. The phenomena are strongly influenced by hydration distribution in the PEM. Additionally, the use of environmentally harmful fluorocarbon-based membranes in fuel cells and electrolyzers is currently questioned, and novel hydrocarbon-based membranes are expected to replace them. In this project, we aim to characterize the dynamics of both water and ion transport in poly-electrolyte membranes on different length scales. To gain insights into the factors controlling fuel cells and electrolyzers´ durability, the proposed project combines novel experimental techniques, such as in-operando visualization and ex-situ and post-mortem membrane characterization, with numerical simulations. A microfluidic model system will be employed to study transport phenomena at the microscale. A larger cell, comprising identical membrane and electrode material as classical laboratory-scale setups, will provide insights into the effects of hydration level and act as a bridge between microfluidics and the bench-top scale. In bench-top cells, both conventional fluorocarbon and novel hydrocarbon PEM will be tested to compare electrochemical performance, PEM hydration, and catalyst and membrane degradation. Additionally, simulations will aid in the comparison and interpretation of microscale and macroscale results. For in-situ characterization of water and ion transport in the microfluidic cells, mainly fluorescence-based imaging methods will be used. For the benchtop scale, more traditional methods for membrane and cell characterization will be employed, including water uptake and proton conductivity measurements for the membrane, as well as electron microscopy and elemental analysis of membrane-electrode assemblies. By understanding the fundamentals of transport processes at micro and macro scales, our proposed novel experiments will directly contribute to the design and development of new materials and the identification of perational strategies to mitigate the degradation of PEM fuel cells and electrolyzers.