Porous Transport Layers for Anion Exchange Membrane Water Electrolysis: The Impact of Morphology and Composition.

Anion exchange membrane water electrolysis (AEMWE) is an emerging technology for the low-cost production of hydrogen. However, the efficiency and durability of AEMWE devices is currently insufficient to compete with other low-temperature electrolysis technologies. The porous transport layer (PTL) is a critical cell component that remains relatively unoptimized for AEMWE. In this study, we demonstrate that device performance is significantly affected by the morphology and composition of the PTL. For Ni fiber-based PTLs with a ∼2 μm CoO oxygen evolution reaction catalyst layer, decreasing the pore size and porosity resulted in a 20% increase in current density at 2 V in 1 M KOH supporting electrolyte. Alloy PTLs with even lower porosity had a higher performance; in particular, the stainless steel PTL gave an 80% increase in current density relative to Ni. Without CoO, the alloy PTLs still demonstrated high activity, indicating that the PTL material was catalytically active. However, characterization of the electrode and electrolyte after testing indicated that the alloy PTLs also underwent restructuring and corrosion processes that may limit long-term stability. This study demonstrates that the design of PTLs with improved morphology and composition is an important area of focus to achieve AEMWE performance targets.