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State-of-the-art industrial electrocatalysts for the oxygen evolution reaction (OER) under acidic conditions are Ir-based. Considering the scarce supply of Ir, it is imperative to use the precious metal as efficiently as possible. In this work, we immobilized ultrasmall Ir and Ir0.4Ru0.6 nanoparticles on two different supports to maximize their dispersion. One high-surface-area carbon support serves as a reference but has limited technological relevance due to its lack of stability. The other support, antimony-doped tin oxide (ATO), has been proposed in the literature as a possible better support for OER catalysts. Temperature-dependent measurements performed in a recently developed gas diffusion electrode (GDE) setup reveal that surprisingly the catalysts immobilized on commercial ATO performed worse than their carbon-immobilized counterparts. The measurements suggest that the ATO support deteriorates particularly fast at elevated temperatures.

The polymer electrolyte membrane (PEM) water electrolysis is a promising technology for the production of hydrogen from water using fluctuating renewable electricity sources. However, to achieve widespread application, the investment cost has to be lowered considerably. For optimal two-phase mass transport of gases and water, and to simultaneously ensure electron transfer, a porous transport layer (PTL) is used in PEM systems. Due to the highly oxidative conditions in the oxygen-evolving electrode, PTLs consists of porous titanium, sometimes coated with noble metals to increase corrosion stability. Polymer compounds offer a great potential in terms of cost-efficiency, material properties, which can be easily tailor-made by e.g. polymer additives, and in terms of individual shaping options during the component production in particular by additive manufacturing. However, the conditions in the electrolysis cells are challenging for polymeric materials, in particular for materials used in the oxygen-evolving electrode. Here, we present first steps to a new concept of electronically and protonic conductive polymer structures for the PEM water electrolysis produced by 3D-printing.