Determining the change in performance from replacing a separator with an anion exchange membrane for alkaline water electrolysis

Abstract

Abstract The emphasis on energy storage has caused renewed interest in alkaline water electrolysis (AWE), where the novel anion exchange membrane (AEM) has opened new pathways to further improve this mature technology. The comparison between the novel and the mature is most commonly performed on uneven grounds, as the ionic conductivity of the 30 wt.% (6.89 M) KOH electrolyte used in AWE is significantly greater than the 1.0 M employed in AEM water electrolysis. Through this paper, the performance of a zero-gap water electrolyser is systematically tested utilising either a separator or an AEM in a 1.0 M KOH electrolyte over several temperatures. Catalysed with only untreated nickel foam, the cell configuration with the AEM displayed predictably enough a notably lower series resistance and thereby a lower overpotential. However, the cell with the separator displayed better innate thermal stability, and showed stable results at 25°C, 40°C and 70°C. These findings exhibit the potential of additional R&D efforts in both separators and AEMs.