Reducing interfacial resistances in proton exchange membrane water electrolysis via gas diffusion layer-based layer-by-layer coating

Efficient membrane electrode assembly (MEA) fabrication is essential to reduce voltage losses in proton exchange membrane (PEM) water electrolysis. However, conventional assembly techniques often result in discrete membrane-electrode interfaces that increase contact resistance. Here, we systematically compare traditional decal transfer and catalyst-coated membrane methods with integrated layer-by-layer (LbL) architectures using self-cast membranes as a common reference to isolate fabrication effects. Sequential wet-on-dry coating of the cathode catalyst layer, membrane dispersion, and anode catalyst layer directly onto a gas diffusion layer (GDL) reduces the area-specific ohmic resistance by 60% (45.2 vs. 112 . 5 m Ω cm 2 ) relative to the decal-transferred reference, enabling 1 . 63 V at 1 . 0 A cm − 2 ( 120 mV lower than the decal transferred sample using a selfmade membrane). In addition, eliminating hot pressing preserves a more porous catalyst-layer morphology and lowers the kinetic overpotential. Cross-sectional microscopy reveals a 3D interfacial transition zone, including catalyst penetration into the GDL microporous layer, consistent with reduced electronic and ionic contact resistances. These results identify interfacial architecture as a practical lever for improving PEMWE MEA performance while simplifying manufacturing workflows. • A monolithic PEMWE MEA was fabricated via sequential layer-by-layer GDL coating. • GDL-LbL reduced interfacial resistance by 68% compared to decal transfer. • Omitting hot-pressing preserved catalyst porosity and enhanced mass transport.