Impact of Substrate Type and Membrane Scaling on Catalyst Transfer Efficiency in PEM Water Electrolyzers via the Decal Method

Catalyst‐coated membranes (CCMs) were fabricated using the decal transfer method to enhance catalyst transfer efficiency, performance, and stability in polymer electrolyte membrane water electrolyzers (PEMWEs). Nafion 117 and Nafion 212 membranes with active 5, 25, and 36 cm 2 areas were used, incorporating IrO 2 (anode) and Pt/C (cathode) catalysts. Catalyst inks were sprayed onto PTFE sheet, Kapton film, and Teflon‐coated fiberglass substrates, followed by hot‐pressing at 130°C and 700 psi for 5 min. A thin Nafion ionomer layer facilitated efficient catalyst transfer. Among the substrates, Teflon‐coated fiberglass achieved the highest transfer efficiency (> 95%) and uniform catalyst distribution. At 60°C and 2.0 V, the 5 cm 2 Nafion 212 and Nafion 117 CCMs delivered maximum peak current densities of 1791 and 1497 mA/cm 2 , respectively. While Nafion 212 showed higher initial performance due to its lower thickness and resistance, Nafion 117 demonstrated superior durability during 48‐h stability testing, particularly at larger membrane sizes. These results underscore the potential of the decal method for scalable CCM fabrication and highlight the importance of membrane thickness and substrate selection in developing high‐performance, durable PEMWE systems for hydrogen production.