Hydrocarbon ionomer/polytetrafluoroethylene composite membranes containing radical scavengers for robust proton exchange membrane water electrolysis

A hydrocarbon-based composite membrane incorporating radical scavengers is successfully fabricated using sulfonated poly(arylene ether sulfone) copolymers with a 50 % sulfonation degree (SP50), porous polytetrafluoroethylene (PTFE) substrates, and cerium oxide (CeO₂) nanoparticles for proton exchange membrane water electrolysis (PEMWE). The CeO₂ nanoparticles are uniformly dispersed in the SP50 solution through a ball milling, and the PTFE substrate is treated with n-propyl alcohol to improve the interfacial compatibility between the SP50/CeO₂ solution and PTFE. Additionally, a five-layered structure incorporating two PTFE layers is employed to form robust interlocking interfaces between SP50 and PTFE. Consequently, the composite membrane with CeO₂ exhibits excellent dimensional stability, mechanical properties, and a 3.8-fold reduction in hydrogen permeability as compared with that of the Nafion 212 (N212) membrane. In the hydrothermal tests, the composite membrane demonstrates excellent chemical stability due to the inclusion of CeO₂. During PEMWE operation, the cell performance of the composite membrane is 7.42 A/cm² at 1.9 V, surpassing those of SP50 (5.95 A/cm²) and N212 (5.66 A/cm²). Over the course of the durability test, the composite membrane exhibits the lowest degradation rate (DR). Furthermore, the molecular weight of the composite membrane decreases by only 5 %, significantly outperforming SP50, which shows a 50 % reduction. Therefore, the composite membrane with a radical scavenger provides excellent physical and chemical stability for PEMWE applications.