Ordered Nafion Composite Membranes Doped with Ce-UiO-66: Improved Performance and Decreased H ₂ Crossover in PEM Water Electrolysis

Proton exchange membrane water electrolysis (PEMWE) exhibits significant advantages in renewable energy utilization; however, its performance is still constrained by limited proton transport capability and restricted triple-phase catalytic reaction interfaces. To address these challenges, an ordered composite membrane doped with MOF (R_Nafion-M-O) is proposed to simultaneously enhance proton transport and expand the triple-phase reaction interface, and the respective roles of MOF doping and three-dimensional ordered arrays on performance enhancement are comparatively investigated. Microstructural characterizations demonstrate that an AAO template successfully constructs a three-dimensional ordered Nafion array on the membrane surface, which not only enlarges the anodic triple-phase reaction interface but also establishes fast proton transport pathways. Ce-UiO-66 is uniformly dispersed within the composite membrane, leading to a more homogeneous distribution of ionic clusters and facilitating the construction of interconnected hydrophilic domains. These features result in a simultaneous increase in membrane proton conductivity and effective triple-phase reaction interface, thereby significantly improving electrolyzer performance, with a current density reaching 4.12 A/cm² at an operating voltage of 2 V. In addition, MOF doping combined with the ordered array structure markedly mitigates hydrogen crossover in the electrolyzer. During 300 h of continuous operation, the electrolyzer exhibits the lowest voltage degradation rate (44.8 μV/h) and the lowest increase rate of hydrogen fraction in oxygen (6.28 × 10⁻⁴/h), demonstrating that the proposed composite membrane enables efficient, safe, and stable operation of PEM electrolyzers.