Versatile Decal‐Transfer Method for Fabricating and Analyzing Microporous Layers in Polymer Electrolyte Membrane Water Electrolysis

Abstract Polymer electrolyte membrane water electrolysis (PEMWE) is hindered by the reliance on expensive iridium‐based catalysts. To address this economic challenge, minimizing iridium usage while maintaining performance and durability is imperative. Achieving this goal requires enhanced catalyst utilization through improved electron, ion, and mass transport within the anode. Recent research has increasingly emphasized the development of microporous layers (MPLs) as a key strategy for enhancing the interface between the porous transport layer (PTL) and the catalyst layer (CL). However, standardized methodologies for MPL design and fabrication remain elusive. In this study, a decal‐transfer method is presented as an effective method for introducing a uniform, thin MPL at the CL/PTL interface. By varying the MPL properties, including pore size, thickness, and back‐layer structure, two‐phase transport phenomena are investigated and established guidelines for optimal MPL design. The findings reveal that smaller micrometer‐scale pores in the MPL enhance catalyst utilization and strengthen water capillary force, thereby reducing kinetic and transport overpotentials. Moreover, it is demonstrated that, unless the back layer hinders the in‐plane mass transport beneath the flow field, its structural configuration has minimal influence on electrolysis performance. These results underscore the importance of the CL/PTL interface in determining the overall efficiency of PEMWE systems.