Rational self-supported electrode design with optimized ion migration and gas diffusion for efficient anion exchange membrane water electrolyzer

Abstract

Ion migration and gas diffusion are two of the most critical topics in water electrolysis. Many self-supported electrodes (SSEs) exhibit efficient performance in fundamental research studies due to their excellent gas diffusion. However, such performance is not guaranteed in large-scale electrolyzers due to the extremely large ion-migration resistance of these SSEs. Here we find that a commercial SSE (Ni foam) exhibits efficient performance in fundamental research but performs poorly in an anion exchange membrane water electrolyzer (AEMWE). Further investigations reveal that the poor performance of the AEMWE originates from the large ion-migration resistance caused by the long OH⁻ migration distance within the SSE. After its design is optimized to minimize the ion-migration resistance and enhance gas-diffusion efficiency, the AEMWE is found to deliver a current density of 1 A/cm² at 1.778 V in 1 M KOH at 65 °C. A triple-cell stack is further assembled and found to reach 1 A/cm² at 5.464 V and to exhibit excellent stability over 216 h in 1 M KOH, showing its good potential for scalable production.