Scalable Multilayer PTFE-Reinforced Membranes for Durable, High-Current-Density Hydroxide Exchange Membrane Water Electrolysis in Dilute Alkali.

Hydroxide exchange membrane water electrolysis (HEMEL) is a promising route to cost-effective green hydrogen using renewable energy, yet its commercial potential is hindered by insufficient performance and durability. Here, we address this challenge with an ultrathin, multilayer membrane design that integrates polytetrafluoroethylene (PTFE) reinforcement with low glass-transition temperature (Tg) polymers. Fabricated via a scalable hot-pressing process, these membranes (QPS-PTFE3-nL, n = 3, 4, 5) exhibit anisotropic hydration, alkali stability, and favorable interfacial resistance. This integrated architecture enables stable operation in a 0.1 M KOH dilute electrolyte. The HEMEL employing the optimized QPS-PTFE3-5L membrane achieves an outstanding current density of 3.7 A cm-2 at 1.8 V and demonstrates remarkable durability, operating continuously at 2.0 A cm-2 for over 3300 h-representing state-of-the-art performance in this field. Post-test analysis reveals that performance decay primarily stems from cathode catalyst layer degradation rather than membrane failure, underscoring the robustness of the membrane design. The scalability of this approach is validated by a 160 cm2 cell that maintains stable operation for 52 days under intermittent cycling. This work provides a straightforward and scalable membrane strategy to realize durable, high-performance HEMEL systems.