Design strategies for porous transport layers in anion exchange membrane water electrolysis: materials, structures and advanced manufacturing concepts

Anion exchange membrane water electrolysis (AEMWE) is a promising technology for sustainable hydrogen production. It combines the advantages of alkaline and proton exchange membrane electrolysis, and enables the use of abundant catalyst and structural materials. While significant progress has been made in catalyst development, porous transport layers (PTLs) have received comparatively little attention, despite playing a crucial role in controlling charge transport, reactant distribution, gas removal and overall cell efficiency. This review provides a comprehensive overview of the current state of PTL research for AEMWE, emphasising the relationship between structural design and electrochemical performance. First, the review discusses the fundamental transport mechanisms and functional requirements of PTLs, highlighting the interplay between porosity, pore size distribution, tortuosity, wettability, electrical conductivity, mechanical stability and corrosion resistance. Next, recent advances in PTL materials are critically assessed, including nickel-, stainless steel-, titanium-, and carbon-based systems, as well as structural concepts such as foams, fibre-based materials, wire meshes, additively manufactured architectures, and surface-engineered transport layers. Finally, the review identifies current challenges regarding structural optimisation, long-term durability, standardised evaluation protocols and scalable manufacturing. The analysis suggests that future progress in AEMWE will increasingly depend on rational PTL engineering rather than on catalyst optimisation alone. The development of multifunctional, hierarchically structured transport layers with tailored transport pathways is expected to play a key role.