Anisotropically Wettable Porous Transport Layers for Gas Management in Water Electrolyzers

Conventional studies on water electrolysis have primarily focused on designing novel electrocatalysts and membranes, with intrinsic properties closely linked to the immediate performance of water electrolyzers. However, less attention is directed toward porous transport layers (PTLs), which are essential for sustaining efficient, long-term, high-current operation by enabling effective mass transport. Here, a novel PTL with anisotropic wettability (AW-PTL) is introduced to enhance the efficiency of anion exchange membrane water electrolyzers (AEMWEs). By hydrophobically modifying the upper half of hydrophilic Ni foam with polytetrafluoroethylene using a simple spray-coating method, anisotropic wettability is achieved, enabling the directional transport of liquid electrolytes and gaseous products. This design significantly improves AEMWE efficiency by facilitating the removal of gas bubbles, which typically block catalyst active sites and hinder electrolyte supply. The method is universally applicable across conventional PTL types and demonstrates scalability to large-area (up to 225 cm²) and short-stack AEMWEs. This work advances the practical application of water electrolysis, providing an adaptable solution for other water electrolyzer types using existing catalysts and membranes.