On-site crosslinked quaternized poly(vinyl alcohol) as ionomer binder for solid alkaline fuel cells

Abstract

Water-soluble polyvinyl alcohol functionalized with quaternary ammonium groups and crosslinked quaternized polyvinyl alcohol were synthesized and used to prepare an ionomer binder solution having a low boiling point and high dielectric constant solvent to be used in electrodes for solid alkaline fuel cells. The polyvinyl alcohol was quaternized to have anion-conducting ability using glycidyltrimethylammonium chloride. To prevent washing-out of the water-soluble anion-conducting ionomer during fuel cell operations, the quaternized poly(vinyl alcohol) was successfully crosslinked by using an on-site crosslinking method. The highest ionic conductivity of the ionomer was 2.3 × 10−2 S cm−1, and its ion exchange capacity was 1.2 meq g−1 at room temperature. The electrodes were fabricated by a spray method on anion-exchangeable membranes, and membrane-electrode assemblies were operated at 50 °C in ambient pressure and were characterized by voltage–current relationship and cyclic voltammetry. The highest performance of the membrane-electrode assemblies having the electrode with the ionomer of 25 wt.% in dry weight basis was 172.8 mW cm−2 at 0.485 V. As a result, the anionic binder electrodes introduced by the on-site crosslinking were successfully functioned both to conduct OH− ions between electrodes and an electrolyte and to move electron to an external circuit by forming three phase boundary at the electrode of the membrane-electrode assemblies.