Quinuclidinium-Based Microporous Anion Exchange Membranes for Water Electrolysis

Anion exchange membrane water electrolysis (AEMWE) is a promising green hydrogen production method; however, it is constrained by the moderate OH^- conductivity and inadequate alkaline stability of anion exchange membranes (AEMs). Here we report a series of quinuclidinium-based AEMs with branched and microporous structures, achieving 99.95% OH^- conductivity retention after 3100 h in 10 M NaOH at 80 °C. By tuning the rigidity of the branching units to limit chain packing, micropores were created to enhance OH^- transport, which improved the diffusion coefficient of OH^- by 1.6 times within the poly (terphenyl-triptycene-quinuclidinium) (PTPQ-Trip) membrane having the most rigid structure. An AEMWE configured with a PTPQ-Trip membrane and nickel-alloy catalysts can tolerate varied alkaline concentrations and deliver a hydrogen production current density of 2.8 A cm^-2 at 2.0 V in 5 M KOH, which can be continuously operated at 0.5 A cm^-2 and 30 °C for over 1200 h, with intentionally included stop/start interruptions. The assembled AEMWE demonstrated stable operation for 1400 h under alternating operational current densities and varying electrolyte temperatures. This work underscores the critical role of alkaline-resistant microporous AEMs and highlights the adaptability of AEMWE for hydrogen production using renewable electricity.