Integrated-Channel Porous Transport Layers Reduce Ohmic and Mass Transport Losses in Polymer Electrolyte Membrane Electrolyzers

Abstract

To mitigate the impacts of anthropogenic climate change, clean energy storage solutions such as hydrogen produced via polymer electrolyte membrane water electrolysis (PEMWE) are critically required. However, the porous transport layer (PTL) in current PEMWE systems lacks optimization of through-plane and in-plane transport properties. In this work, a PTL design with integrated channels (IC-PTL) to improve the PTL/flow channel interface and provide additional pathways for in-plane flow is proposed. As current density increases, the IC-PTL reduces mass transport overpotentials by up to 71.4% compared to the baseline PTL (B-PTL) assembly due to shorter mass transport pathways. Moreover, the IC-PTL lowers ohmic overpotentials at high current densities by up to 42.8% due to improved interfacial contact and enhanced membrane hydration. Membrane hydration is further quantified via X-ray synchrotron radiography analysis of changes in membrane thickness and X-ray transmission through the membrane, revealing that the IC-PTL assembly displays a consistently thicker membrane and recovers from thinning faster than the B-PTL assembly. Furthermore, membrane hydration is impacted more at the catalyst layer interfaces than in the center of the membrane. As such, the addition of in-plane transport pathways to next-generation PTL designs to improve membrane hydration and mass transport is recommended.