Iron as a key contributor in stability investigations of alkaline water electrolysis electrodes

Alkaline water electrolysis (AWE) holds great potential for sustainable hydrogen production. However, further industrially relevant research is crucial for bridging the gap toward industrial application. Here, one important aspect is the understanding and improvement of the stability of AWE electrodes under high current densities. In this context, we report that dissolved iron (Fe) in the electrolyte, besides enhancing the short-term performance of nickel (Ni)-based electrode materials, significantly affects their stability. We demonstrate that, during operation, Fe is deposited on the cathode, whereas during shutdown, it leaches back into the electrolyte. This reversible Fe-deposition process significantly enhances the long-term performance of cathodes in high Fe-containing systems (>10 ppm). Ni anodes, concurrently, undergo a reversible deactivation over operation time as fewer Fe sites are available to establish the dynamic Fe-Ni equilibrium. Hence, dissolved Fe significantly affects the Ni-electrode stability, which is an often-overlooked aspect in catalyst research.