Hydrogen Electrolyzer Recycling - Characterization of the layers and particle components of membrane electrode assemblies to assess the ultrafine particle separation ability

In water electrolyzer cells, active materials contain various fine-grained critical raw materials such as platinum group metals or rare earth elements. Although the readiness level of water electrolysis technology is high and large scale of hydrogen production is targeted worldwide, there has been no significant research on recycling of end of life (EOL) water electrolyzer cells. For a functioning circular economy, recycling processes for these valuable materials have to be developed especially on the fine particle scale below 100 μm.
The in-depth characterization of water electrolyzer cells and their components allows to assess their liberation behavior and subsequent separability based on different particle properties, e.g. size, density, wettability, etc. Thus, this paper aims at identifying the material composition and properties of proton exchange membrane electrolyzer cell (PEMEL) and high temperature electrolyzer cell (HTEL) before processing. In PEMEL, critical raw materials such as iridium, ruthenium, and platinum are used, while nickel, lanthanum, and yttrium are used in HTEL. Techniques such as automated mineralogical analysis (MLA), X-ray fluorescence spectroscopy and microscopy (XRF) and laser diffraction are used to identify the possibility of liberation. To ensure a high recovery rate of critical raw materials, the surface properties of individual component have been studied. Additional contact angle studies by means of pressed bubble and the particle attachment on single air bubbles revealed the wettability of membrane electrode assemblies and significant differences between the components. Furthermore, pH and salinity show to influence the wetting behaviour of the components. These findings provide the design of the separation study for EOL electrolyzer cells.