Ultraviolet-Activated Solid-State Nitrene Cross-Linking: A Scalable Pathway to Prolonged Lifespan in Anion Exchange Membranes

Abstract

Anion exchange membranes (AEMs) offer a costeffective alternative to proton exchange membranes as alkaline fuel cells and electrolyzers permit the use of non-platinum group electrodes and components. Despite continued progress, the operational lifetime and stability of these membranes limit the widespread adoption of AEM-based electrochemical technologies. This study presents a flexible and easily implemented ultraviolet (UV)-initiated nitrene-based cross-linking method which uses a small, facile organic azide precursor. As a proof of concept, we demonstrate this approach on the well-studied poly(2,6-dimethyl-1,4-phenylene oxide) quaternary ammonium AEM (QPPO) polyelectrolyte. A survey of cross-linker density (2.5−10 mol %) found that the addition of 10 mol % results in a 59% reduction in water uptake, a 58.8% decrease in the swell ratio, and a 31% increase in tensile strength vs the un-cross-linked material. Nitrene cross-linking also enhanced the membrane's durability, enabling 1000 h of stable performance under electrochemical load. This UVinitiated cross-linking method may be easily integrated into production processes, allowing chemical cross-linking at any stage, including posthydration.

Degradation of Anion Exchange Membranes by Cation Elimination: Impact on Water Uptake, Nanostructure, and Ionic Mobility

“…The membranes of this study are modeled with polymers with a degree of polymerization (DP) 21. This DP is an order of magnitude shorter than the one in the experiments, which typically have DP 200–350 (molecular weight 30,000–50,000 g mol –1 ). ,, SI Section 3 presents our analysis of the ionomer peak, pore size distribution (PSD), and pair correlation functions of undegraded PPO-TMA membranes with DP 20 and 200 with DF 50% prepared and equilibrated in cells with ∼16 nm side in ref . Our analysis shows that the properties of DP 20 and DP 200 are indistinguishable.…”