Elucidating effects of catalyst loadings and porous transport layer morphologies on operation of proton exchange membrane water electrolyzers

Producing green hydrogen efficiently via proton exchange membrane water electrolysis (PEMWE) is the key for achieving decarbonization targets. Iridium catalyst is expensive, and it is important to minimize its use and to optimize interface between Ir and ionomer or water for higher utilization of catalyst in oxygen evolution reaction. In this paper, x-ray computed tomography along with electrochemical and modeling techniques are used to characterize the interface for two different porous transport layers (PTLs) and catalyst layers at various loadings. We show that low porosity sintered PTLs exhibit higher interfacial contact with the catalyst and the membrane that results in improved kinetics. Radiography and modeling results indicate that oxygen taking multiple transport pathways through the PTL results in slug flow through the channels that reduces mass transport overpotential. Based on the results, we suggest design guidelines for high efficiency and durable PEMWE and their components. Probing interfacial characteristics in polymer electrolyte water electrolyzers using x-ray computed tomography along with electrochemical techniques offers insight into the electrochemically active area. Engineering these interfaces increases the catalyst utilization and durability at low loadings and results in efficient gas transport leading to enhanced operation and subsequent reduction in cost. • X-ray CT is used to study the nature of anodic interfaces in PEM electrolyzers. • Catalyst utilization and gas transport are affected by the nature of the interface. • Low loaded electrodes had durability issues, optimal loading around 1 mg cm − 2 . • 80% gas saturation in channels found to be optimal for enhanced mass transport.