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

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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.