Localized CeO2-assisted radical suppression in hydrocarbon-reinforced membranes for durable water electrolysis

The chemical degradation of proton exchange membranes (PEMs) in proton exchange membrane water electrolysis (PEMWE) is primarily caused by the reactive oxygen species generated at the cathode, which attack the ionomer structure and compromise long-term durability. In this study, an asymmetrical hydrocarbon-based (HC) reinforced composite membrane is fabricated by selectively localizing cerium oxide (CeO 2 ) nanoparticles—a radical scavenger—on the cathode-facing side to maximize radical quenching efficiency while minimizing inorganic additive content. The membrane is constructed as a five-layer structure using sulfonated poly(arylene ether sulfone) copolymers with a 50 % sulfonation degree (SPAES50) and porous polytetrafluoroethylene (PTFE) supports to enhance mechanical strength and dimensional stability. The asymmetrical configuration effectively suppresses hydrogen crossover, exhibits lower water uptake, and improves the dimensional stability compared to pristine SPAES50. Among the prepared membranes, the composite membrane with 5 wt% CeO 2 layer on the cathode-facing side demonstrates the optimal properties of proton conductivity (0.154 S/cm at 80 °C), hydrogen permeability (37.3 barrer), and durability, retaining 99 % of its initial cell performance after operating 200 h at 2 A/cm 2 . These results confirm that the targeted localization of radical scavengers on the cathode-facing side, combined with PTFE reinforcement, is an effective strategy for developing durable HC-based PEMs for PEMWE applications. • Asymmetric hydrocarbon composite membrane with CeO 2 localized on cathode side. • Porous PTFE supports enhanced membrane mechanical strength and dimensional stability. • Composite membrane showed lower H 2 permeability and higher stability vs SPAES50. • CeO 2 on cathode side enhanced radical scavenging and PEMWE durability. • Optimized F/SP-C5 showed highest PEMWE performance with 99 % retention at 200 h.