Effects of hydrolysis degree on ion-doped anion exchange membranes in direct borohydride fuel cells.

Herein, polyvinyl alcohol based anion exchange membranes (AEMs) doped with various cobalt and chloride salts are synthesized to investigate the structure-performance relationship of ion-doped AEMs systemically. The performances of ion-doped AEMs are found to be related to the hydrolysis degree (DH) of the doped anions and cations. It is found that cations with varying DH transformed into hydroxides with different sizes and dispersions, which plays a key role in determining the structures and properties of cation-doped AEMs. On the other hand, weak-acid anions remained in the AEMs after alkali immersion, hindering OH− conduction and leading to the degradation of the anion-doped AEMs. High DH cations mildly react with the matrix and transform into more dispersive complexes, while low DH anions are replaced by OH−.The direct borohydride fuel cell using CuCl 2 -doped AEM exhibits a maximum power density of 202.4 mW cm−2 at 30 °C. [Display omitted] • The properties of ion-doped AEMs are effected by the DH of doped-ions. • Cations transform into hydroxides with various sizes in the cation-doped AEM. • Weak-acid anions stay in the anion-doped AEM and hinder the OH− conduction. • Mildbase strong-acid salts are concluded as the most promising ionic additives. [ABSTRACT FROM AUTHOR]