Determining decoating efficiency for mechanically stressed catalyst coated membranes of proton exchange membrane water electrolysers.

The recovery of critical raw materials from water electrolysers, which are used to produce green hydrogen, is essential to keep the raw materials with limited availability in the material cycle and to facilitate the expansion of production of this technology, which is supposed to be essential for the decarbonisation of our industrial society. Proton exchange membrane water electrolysers (PEMWE) use precious metals such as Ir and Pt as catalysts, which require a high recycling rate due to their natural scarcity. In order to investigate at an early-stage mechanical recycling technologies, such as shredding for liberation and milling for decoating of these complex materials, it becomes necessary to develop small-scale experimental methods. This is due to the low availability of End-of-Life samples and the high price of pristine electrolyser components. Especially decoating has shown huge potential for a highly selective separation of defined material layers; nevertheless, until now, there is no method to determine the success of decoating of the flexible polymer membrane, which is coated on both sides with particle-based electrodes. One possible concept is presented here, using scanning electron microscope images and micro-X-ray fluorescence elemental maps. Image processing and segmentation is performed using the WEKA software and a simple thresholding method. This allows the efficiency of the decoating process to be determined with an accuracy of ±0.5 percentage points for decoated PEMWE cell samples. The high accuracy of the presented method framework provides the necessary tool for any further quantitative development of improved mechanical stressing for decoating.