The Impact of Iron Impurities on the Activity and Stability of Nickel Electrodes in Liquid Alkaline Water Electrolysis

Liquid alkaline water electrolysis (LAWE) offers a promising pathway to low-cost hydrogen production by leveraging earth-abundant metals to achieve both economic and environmental sustainability. 1 However, ensuring the durability and efficiency of LAWE systems requires a detailed understanding of the impact of impurities, particularly iron. 2 Iron contamination can originate from various sources, including leaching from stainless-steel components in the balance of plants, impurities in the KOH, and water supply. In this study, we investigate the influence of iron impurities on LAWE performance using a single-cell configuration with separate anolyte and catholyte streams. This design allows us to isolate the effects of iron on each half-reaction. Remarkably, adding just 10 ppm of iron to a 30 wt% KOH electrolyte leads to a substantial enhancement in electrochemical activity. Performance improvements are observed when iron is introduced to either the anolyte or catholyte independently, with the greatest gains achieved when iron is added to both electrolytes simultaneously. Additionally, this work highlights the critical influence of electrode morphology on the cell performance with and without added iron, comparing densely structured nickel porous transport layers, intermediate nickel foam, and less dense woven nickel mesh. Ex-situ characterization reveals significant morphological and chemical transformations, including the formation of active NiFe oxyhydroxide and distinct iron deposition patterns. These findings provide valuable insights into cell performance and stability. References S. Shiva Kumar and H. Lim, Energy Reports , 8 , 13793–13813 (2022). H. Becker et al., Sustain Energy Fuels , 7 , 1565–1603 (2023).