Polymer anion-selective membranes for electrolytic splitting of water. Part II: Enhancement of ionic conductivity and performance under conditions of alkaline water electrolysis

Abstract

An attempt was made to increase the ionic conductivity of novel, heterogeneous, anion-selective membranes by increasing the porosity of their surface skin. This was based on the addition of a water-soluble component, namely poly(ethylene-ran-propylene glycol), to an inert polymer matrix, based on low-density polyethylene, while mixing it with the ion-exchange particles. A series of membranes was prepared, consisting of 66 wt% of anion-exchange phase represented by a styrene-divinyl benzene copolymer matrix with quaternary ammonium functional groups and an inert polymer matrix in a mixture with variable amounts of water-soluble component added. The membranes were subsequently tested with respect to their morphology, mechanical properties, apparent ion-exchange capacity, ionic conductivity, and performance under conditions of alkaline water electrolysis. When added in the appropriate amount, the addition of a water-soluble component was found to improve the electrochemical properties of the resulting membrane efficiently, while at the same time not reducing its mechanical properties to below a critical level.