Hydroxide Transport in Next Generation Anion Exchange Membranes

Anion Exchange membranes (AEMs) are being developed for a variety of applications. Among these are fuel cells and electrolyzers that require the AEM to conduct hydroxide anions. Measurement of the ionic conductivity of hydroxide is challenging because the hydroxide is a strong nucleophile and attacks polar groups in the AEM and also rapidly reacts with atmospheric CO 2 to form the less conductive carbonate and bicarbonate counter anions. We have developed a rigorous method to fully exchange AEMs into the hydroxide form while excluding CO 2 and remove all residual inorganic salt from the film prior to measurement. These measurements of the hydroxide ion conductivity coupled with self diffusion measurements of water and the similarly sized fluoride anion in these films are beginning to shed insight into how hydroxide anion transport can be maximized in state of the art AEMs.