Investigating Cathode Ionomer Content and Assembly Techniques for Anion Exchange Membrane Water Electrolyzers

Anion exchange membrane water electrolysis (AEMWE) offers a promising solution for achieving large-scale, low-cost hydrogen production. Optimizing cathode catalyst-ionomer-membrane configurations is crucial for improving AEMWE performance. Herein, cathodes using Pt/C and Sustainion, PiperION, or Nafion with varying content (5–25 wt %) and assembly techniques (catalyst-coated substrates, CCSs, and catalyst-coated membranes, CCMs) are examined to reveal their impact on AEMWE performance. Scanning electron microscopy revealed Nafion produced the most homogeneous catalyst layers and smallest particle sizes. In half-cell testing, 20 wt % Nafion achieved the lowest overpotential of −15.6 mV at 10 mA cm–2 and the highest electrochemical surface area of 83.71 cm2 mg–1Pt/C. The performance trend in CCS was more pronounced than in CCM, as the catalyst layer is deposited layer-by-layer during CCM fabrication and blocks active sites, obscuring any benefits of optimizing the ionomer loading to achieve minimal agglomeration and homogeneity. Additionally, CCS outperformed CCM, achieving lower ohmic and charge transfer resistances. The ideal ionomer content was 15–20 wt % throughout all samples, with 20 wt % Nafion achieving the best performance, owing to the low charge transfer resistance.