(Invited) Hierarchically Structured Electrocatalysts Using Scalable Synthesis Techniques for Membrane Water Electrolyzers

Abstract

Beyond composition, the morphology of catalyst particles is a key-parameter to allow for a high accessibility to catalytic sites but it is also of paramount importance to manage gases and water transport within catalyst layers in membrane-electrode assembly based devices. Besides their electrochemical activity, fabricating high performance catalysts and catalyst layers that are compatible with industry fabrication processes is critical for their implementation in commercial electrochemical devices. Considering these requirements, we are developing green, cheap and scalable solution synthesis techniques to prepare hierarchically structured catalysts that can be readily incorporated into catalyst layers.Two strategies will be discussed. We have recently introduced an aerosol synthesis technique for the preparation of highly porous iridium pure and mixed oxides that are highly active and stable towards the Oxygen Evolution Reaction in acidic media. Beside beeing ideally suited for the preparation of highly porous catalyst layers, the hierarchical morphology can also be used for fundamental studies [1] or used as a probe to follow the catalyst degradation in PEM water electrolysis devices.[2]We also implemented the well-known polyol process [3] to prepare heterofunctional catalysts with ultra-low PGM content that are active towards another challenging reaction in anion exchange membrane water electrolyzer: the Hydrogen Evolution Reaction in alkaline media. The structure-properties relationship in these materials is assessed by a large set of techniques including SEM, XRD, XRF and STEM-EDX as well as surface (XPS) and bulk (XAS) characterizations, including operando XAS. Nature Communications, 2021, 12, 3935, 1038/s41467-021-24181-x Chemistry of Materials, 2023, 35, 20, 8590–8598, 1021/acs.chemmater.3c0152. Chem. Soc. Rev. , 2018, 47, 5187-5233, 10.1039/C7CS00777A