Oxide-Filled Porous Transport Layer in Ordered Membrane Electrode Assembly for Water Electrolysis

The poor interfacial contact between the low-iridium-loaded catalyst layer and the porous transport layer (PTL) remains a major bottleneck for limiting the performance of proton exchange membrane water electrolysis (PEMWE). In this work, a microporous layer (MPL) composed of CeO₂ nanoparticles and microcrystalline cellulose (MCC) was developed to address this challenge. By rationally tuning the particle sizes of CeO₂ and MCC, the resulting infill structure exhibited significantly improved interfacial compatibility and a tailored pore size distribution. Consequently, the ordered membrane electrode assembly (MEA) incorporating this optimized MPL demonstrated an electrochemically active surface area (ECSA) 2.8 times higher than that of a conventional MEA without an MPL filler. Furthermore, the fabricated ordered MEA achieved a high current density of 4.58 A cm^-2 at 2.0 V with an ultralow Ir catalyst loading of 48.4 μg cm^-2 while giving excellent activity retention for over 200 h at 0.5 A cm^-2 current density. This study offers a promising strategy for designing high-performance MEA with ultralow precious metal loading.