Ultra‐Efficient Hydrogen Crossover Suppression Achieved by Precise Pt Hybridization in Thin Nafion Membranes for Water Electrolyzer

Abstract Reducing the thickness of proton exchange membranes (PEMs) is a highly effective strategy to enhance the operational efficiency of proton exchange membrane water electrolyzer (PEMWE). However, this often leads to hydrogen crossover, raising concerns about system stability. Perfluorosulfonic acid (PFSA)‐stabilized Pt nanoparticles (Pt NPs) are synthesized and introduced into fabricate PFSA bilayer membrane. Electron microscopy and scattering analyses confirm the precise localization of Pt NPs within the hydrophilic domains without disturbing the overall membrane morphology. This precise doping strategy enables the on‐site scavenging of the hydrogen diffusing across the membrane at an ultralow Pt loading (0.002 mg cm −2 ). In contrast, conventional Pt doping without a stabilizing matrix induces severe aggregation, restricting nanoparticle entry into hydrophilic domains and resulting in inefficient hydrogen elimination even at elevated loadings. Moreover, the approach significantly enhances operational durability: hydrogen crossover suppression remained stable after 500 h of operation in a practical PEMWE device at current densities of 1.0 and 2.0 A·cm − 2 , confirming the membrane's excellent durability.