Water Uptake Study of Anion Exchange Membranes

Anion exchange membrane fuel cells (AEMFCs) have attracted extensive attention \nin the recent years, primarily due to the distinct advantage potentials they have over the mainstream \nproton exchange membrane fuel cells. The anion exchange membrane (AEM) is the key \ncomponent of AEMFC systems. Because of the unique characteristics of water management in \nAEMFCs, understanding the water mobility through AEMs is key for this technology, as it \nsignificantly affects (and limits) overall cell performances. This work presents a study of the \nequilibrium state and kinetics of water uptake (WU) for AEMs exposed to vapor source H2O. We \ninvestigate different AEMs that exhibit diverse water uptake behaviors. AEMs containing different \nbackbones (fluorinated and hydrocarbon-based backbones) and different functional groups \n(various cations as part of the backbone or as pendant groups) were studied. Equilibrium WU \nisotherms are measured and fitted by the Park model. The influence of relative humidity and \ntemperature is also studied for both equilibrium and dynamic WU. A characteristic time constant is \nused to describe WU kinetics during the H2O sorption process. To the best of our knowledge, this \nis the first time that WU kinetics has been thoroughly investigated on AEMs containing different backbones and cationic \nfunctional groups. The method and analysis described in this work provide critical insights to assist with the design of the nextgeneration \nanion conducting polymer electrolytes and membranes for use in advanced high-performance AEMFCs.