Superaerophobic hydrogels for diaphragm modification to suppress gas crossover in alkaline water electrolyzers

Abstract

Among low-temperature electrolyzer technologies, alkaline water electrolysis (AWE) is the most mature owing to its durability and reliance on inexpensive materials. However, AWEs still face safety concerns arising from gas crossover through porous diaphragms, which can lead to hydrogen accumulation in the oxygen stream and potential explosion risk. Suppressing gas crossover is therefore essential for the safe and scalable deployment of AWE systems. Herein, we present a strategy to control diaphragm wettability using superaerophobic polyvinyl alcohol (PVA) hydrogel coatings that mitigate gas crossover. Gas transport across the diaphragm was quantified through a combination of (i) penetrated oxygen assessment via H-cell oxygen reduction reaction (ORR) current analysis and (ii) direct dissolved oxygen measurements during AWE operation. In addition, gas chromatography analysis of the anode gas phase was performed to directly verify hydrogen crossover. These complementary measurements consistently demonstrate a reduced crossover rate enabled by the hydrogel's superaerophobicity. In situ visualization further reveals rapid bubble detachment from the hydrogel-coated surface, preventing pressure buildup and suppressing bulk gas penetration. Overall, this study introduces a simple, energy-efficient diaphragm modification strategy that directly addresses a key safety challenge in AWE. By improving gas management without compromising electrochemical performance, this approach offers a practical pathway toward safer and more reliable alkaline water electrolysis for industrial hydrogen production.