Low Hydrogen Crossover Poly(Arylene Quinuclidinium) Anion Exchange Membranes for Renewables‐Compatible Water Electrolysis

ABSTRACT Anion exchange membrane water electrolysis (AEMWE) represents a transformative approach to green hydrogen generation, combining the kinetic advantages of alkaline systems with zero‐gap configurations and platinum‐group‐metal‐free catalyst compatibility. Current implementations, however, face major challenges, including device durability, adaptability to fluctuating renewable energy sources, and safety concerns due to hydrogen crossover. In this work, we demonstrate that poly(arylene quinuclidinium) membranes address these challenges through an engineered polymer backbone featuring extended arene units, which effectively enhance dimensional integrity and inhibit gas crossover. Therefore, the hydrogen permeation suppression achieves a remarkably low H 2 ‐in‐O 2 crossover of only 0.53 vol% @0.1 A cm −2 , and delivers a high current density of 8.5 A cm −2 @2.0 V with stable operation over 1250 h. The optimized PQTPQui‐15 membrane demonstrates practical potential in a kilowatt‐level, three‐cell electrolyzer stack. Furthermore, photovoltaic‐integrated systems maintain safe operation (H 2 ‐in‐O 2 < 0.13 vol%) across 0–190% load fluctuations, and respond to sub‐second power transients while sustaining current densities of 0.04−1.91 A cm −2 . These advancements underscore the critical need to enhance the gas barrier properties of anion exchange membranes and establish a new paradigm for durable, rapidly responsive electrolyzers compatible with intermittent renewables.