Unraveling a Novel Degradation Mechanism in Industrial Scale PEM Electrolytic Cells by Multimodal Analysis Based on X-Ray Computed Tomography
Authors: Heume Christine , Dzieciol Krzysztof , Wolf Niklas , Treutlein Leander , Javed Ali , Poc Jean-Pierre , Rein Lukas , Rutsch Yannik , Tasdemir Yasemin , Mehlkoph Tobias , Basak Shibabrata , Borowec Julian , Speer Sebastian , Jovanovic Sven , Danner Yannik , Karyofylli Violeta , Karl André , Jodat Eva , Eichel Rüdiger-A 
Published: December 2024

Proton exchange membrane electrolytic cell (PEMEC) is a key technology in the production of sustainable “green” hydrogen. In such systems, as an electrolyte and physical barrier, a proton exchange membrane (PEM) is applied [1]. Overall, the performance of a PEMEC depends on many factors, such as the catalyst material and its loading, the thickness of electrodes and membrane and the interface roughness for example. While studies have reported changes in PEM microstructures, even in operando [2], there is still limited data regarding process heterogeneity in large industrial-scale cells operating over long periods. However, enhancing the performance and durability of PEMEC is crucial to propel this technology forward, enabling its up-scaling and market introduction on an industrial level.

In this study, we investigated the morphology and degradation mechanisms of membrane electrode assemblies (MEAs) in PEMEC using a multimodal analytical approach. The investigated MEAs, which were operated for 5000 hours, consisted of an Ir coated anode and a Pt cathode and were as large as several hundred cm².

Firstly, the morphology of post-test MEAs was analyzed by the means of X-ray computed tomography (XCT). Here, a measurement protocol provided imaging data at multiple scales. Furthermore, the field-of-view was greatly increased by rolling the MEA and later unwrapping the reconstructed image. A simple, yet robust segmentation algorithm, allowed to automatically delineate features like agglomerates and cracks inside the electrodes post-test. This thorough XCT study led to the
discovery of a novel degradation mechanism in PEMEC, which, to the best of our knowledge, has not yet been discussed in literature. The found morphological anomaly was linked to electrochemical behavior of the cell by analyzing electrochemical impedance spectra (EIS) and measuring the gas permeation through the MEA. Current sensing atomic force microscopy (AFM) was used to analyze the electrical properties in the vicinity of the detected anomalies.

Additionally, metallographic techniques such as focused ion beam scanning electron microscopy (FIB/SEM) and transmission electron microscopy (TEM), combined with energy-dispersive X-ray spectroscopy (EDS) and Raman spectroscopy, provided high-resolution local morphology and the chemical composition within the affected regions. Finally, after collecting all this data, we were able to propose physical 1-D and 3-D models for the observed phenomena and their effects on PEMEC.

In conclusion, this study on a previously unknown degradation mechanism inside MEAs demonstrates the significance of a multimodal analytical approach when it comes to detecting, understanding and mitigating the degradation in PEMEC. Such an approach will further pave the way for enhanced performance and durability in PEMEC on an industrial scale.

[1] B. Han et al., Electrochimica Acta, 2016, 188, 317-326.

[2] E. Leonard et al., Sustainable Energy Fuels, 2020, 4, 921-931.

Figure 1