Evaluating the intrinsic alkaline stability of anion exchange membranes under low-hydration conditions via a vacuum-assisted degradation protocol

Anion exchange membranes (AEMs) are vital for next-generation electrochemical energy devices. However, the long-term alkaline stability of anion conductive polymers remains a critical bottleneck for practical applications. Conventional ex situ chemical stability tests, typically performed in high-concentration alkaline aqueous solutions at high-temperature, often overestimate membrane stability because the hydration shell around hydroxide ions (OH − ) significantly reduces their nucleophilicity. In AEM-based electrochemical energy devices, localized water-lean environments are frequently encountered, where reduced hydration renders OH − significantly more aggressive. To address this discrepancy, we propose a simple vacuum-assisted accelerated degradation protocol to evaluate the intrinsic alkaline stability in water-lean environments. While several AEMs showed high stability in alkaline solutions, the vacuum-assisted tests revealed rapid degradation via Hofmann elimination. The proposed method is particularly valuable for uncovering degradation mechanisms specific to water-lean environments and for accurately evaluating alkaline stability during practical device operation. • A vacuum-assisted degradation test protocol for AEMs is proposed. • The new protocol evaluates intrinsic alkaline stability in water-lean environments. • Water-lean environments accelerate Hofmann elimination in cationic groups. • Designing AEMs without β -protons improves stability in water-lean environments.