Strategies for Lowering Hydrogen Permeation in Membranes for Proton Exchange Membrane Water Electrolyzers and Fuel Cells

Proton exchange membrane (PEM) water electrolyzers and fuel cells are pivotal for renewable hydrogen technologies. The membrane electrode assembly (MEA) is a critical component in both technologies, with the PEM's core functionality-proton conduction coupled with gas impermeability-dictating overall cell performance and durability. One of the key challenges faced by the commercial perfluorosulfonic acid (PFSA)-based PEMs is the high rate of hydrogen permeation, reducing efficiency and raising safety concerns due to hydrogen-oxygen mixing risks. Therefore, there is an urgent need to mitigate hydrogen crossover in PEMs to enhance operational efficiency and ensure cell safety, particularly for the high-pressure electrolyzers. This review commences by elucidating the hydrogen transport mechanisms in PFSA-based PEMs, along with the methodologies employed to measure hydrogen permeation. Subsequently, the recently developed strategies aimed at reducing hydrogen permeation in PEMs are summarized, with a primary focus on PFSA-based membranes, alongside considering advancements in alternative hydrocarbon polymer membranes. Finally, the challenges that remain are discussed, and potential solutions for addressing hydrogen permeation issues in PEM applications are proposed. This review seeks to provide valuable insights for both academic research and industrial applications, in the pursuit of low-hydrogen permeation PEMs specifically designed for water electrolysis and fuel cell technologies.