Communication—Contribution of Catalyst Layer Proton Transport Resistance to Voltage Loss in Polymer Electrolyte Water Electrolyzers

Mass transport losses (η mtx ) play a significant role at high current densities in polymer electrolyte water electrolyzers (PEWEs). Previous work has shown that η mtx depends on the porous transport layer (PTL) structure, although a clear correlation between the material morphology and η mtx has not been established. In this work, we experimentally determine the overpotential η H + CLa associated with the proton transport in the anodic catalyst layer by measuring the ionic resistance in the catalyst layer using electrochemical impedance spectroscopy (EIS) and the transmission-line model. We found that overpotentials, including η H + CLa , depend on the PTL morphologic surface properties.