From cathode hydrophilicity to membrane hydration: Counterbalancing electro-osmotic drag for efficient water electrolysis

Mitigating membrane dehydration caused by electro-osmotic drag is essential for high-current-density proton exchange membrane (PEM) water electrolysis at low catalyst loadings. This study combined overpotential analysis with cathode water-replenishment perturbations to examine how cathode-catalyst macroscopic hydrophilicity and loading regulate membrane hydration. Appropriate hydrophilicity suppressed dehydration and the associated increase in high-frequency resistance (HFR). At 0.1 mgPt cm −2 and 4 A cm −2 , the most hydrophilic catalyst tested reduced HFR by approximately 11% and cell voltage by 81 mV relative to the least hydrophilic catalyst; reduced ohmic overpotential accounted for 59% of this voltage decrease. Increasing loading compensated for insufficient water retention in less hydrophilic catalysts, whereas controlling loading for more hydrophilic catalysts better preserved water–gas transport. Water-replenishment perturbations further verified the dynamic coordination between reverse water transport and electro-osmotic drag. These findings guide the matching of catalyst hydrophilicity and loading in low-Pt cathodes.