AEM Water Electrolysis with Ni-Based Catalysts and Tailored Poly(arylene piperidinium) Materials for Improved Stability

Anion-exchange membrane water electrolysis (AEMWE) is a promising low-temperature technology for hydrogen production. It leverages the advantages of the currently dominant technologies (alkaline water electrolysis and proton-exchange membrane water electrolysis) by using transition metal group based catalysts and a zero-gap configuration, enabling high efficiency. However, current AEMWE systems show a limited stability and efficiency. In this work, commercial and non-commercial polymers are used to fabricate catalyst-coated membranes with a production method oriented towards scalable production (1). A tailored poly(arylene piperidinium) polymer (PAP) shows enhanced stability compared to commercial Aemion+ TM during 100 h operation at 1 A/cm 2 and 60 °C in 1 M KOH electrolyte (Figure 1) (2). Additionally, different anode catalysts are employed and measured in a reference electrode setup to separate the cell voltage into contributions from the anode and cathode (3). Here, the overpotential of Ni(OH) 2 is higher compared to the more active NiFe-layered-double-hydroxide(LDH) and iridium oxide. Employing this setup to measure individual degradation of cathode and anode is part of ongoing research. Figure 1. a) Tailored PAP material compared to Aemion+ TM based systems operated at 1 A/cm 2 showing a linear degradation of ca. 400 µV/h. b) Polarization curves of AEMWE single cells with different anode catalysts, measured with an integrated reference electrode setup, which allows to distinguish anode and cathode contribution to the cell voltage. Measured at 60 °C in 1 M KOH electrolyte, 5 cm 2 cell area. References Koch, S.; Metzler, L.; Kilian, S. K.; Heizmann, P. A.; Lombeck, F.; Breitwieser, M.; Vierrath, S. Toward Scalable Production: Catalyst‐Coated Membranes (CCMs) for Anion‐Exchange Membrane Water Electrolysis via Direct Bar Coating. Advanced Sustainable Systems 2023, 7 (2). DOI: 10.1002/adsu.202200332. Weber, R.; Klingenhof, M.; Koch, S.; Metzler, L.; Merzdorf, T.; Meier-Haack, J.; Strasser, P.; Vierrath, S.; Sommer, M. Meta -kinks are key to binder performance of poly(arylene piperidinium) ionomers for alkaline membrane water electrolysis using non-noble metal catalysts. J. Mater. Chem. A Online 2024, 12 (13), 7826–7836. Xu, Q.; Oener, S. Z.; Lindquist, G.; Jiang, H.; Li, C.; Boettcher, S. W. Integrated Reference Electrodes in Anion-Exchange-Membrane Electrolyzers: Impact of Stainless-Steel Gas-Diffusion Layers and Internal Mechanical Pressure. ACS Energy Lett. Online 2021, 6 (2), 305–312. Figure 1