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最有希望的途径之一。聚合物电解质膜(PEM)燃料电池和PEM电解槽是氢经济的关键技术。要大规模采用这些技术，必须加强稳定的长期运行，并降低成本。控制耐久运转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淋溶对催化剂的电化学活性区域产生了负面影响，降低了整体反应速度，导致了性能损失。更具体地说，催化剂金属离子从催化层移动到PEM，以及它们的再沉积，被认为是至关重要的，但描述得很少。这一现象受PEM中水化分布的强烈影响。此外，在燃料电池和电解槽中使用环境有害的氟碳基膜目前受到质疑，新型碳氢化合物基膜有望取代它们。在这个项目中，我们的目标是在不同的长度尺度上表征水和离子在聚电解质膜中的传输动力学。为了深入了解控制燃料电池和电解槽耐久性的因素，拟议的项目将新的实验技术与数值模拟相结合，如术中可视化和离体膜和死后膜表征。微流体模型系统将被用来研究微观尺度上的输运现象。一个更大的电池，由与经典实验室规模设置相同的膜和电极材料组成，将提供对水合水平影响的见解，并在微流体和台式规模之间起到桥梁作用。在台式电池中，将测试传统的碳氟化合物和新型碳氢化合物PEM，以比较电化学性能、PEM水化以及催化剂和膜的降解。此外，模拟将有助于比较和解释微观和宏观的结果。对于微流控细胞中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，将使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传输过程的基本原理，我们提出的新颖实验将直接有助于新材料的设计和开发，以及确定减缓PEM燃料电池和电解槽降解的操作策略。

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.