Exploring the effect of ion concentrations on the electrode activity and stability for direct alkaline seawater electrolysis

Studying the electrode activity and stability changes caused by the increasing ion concentration during the alkaline seawater electrolysis is crucial to exploit industrial-level seawater electrolyser. Herein, the concentration of hydroxide ion (OH-), chlorine ion (Cl-), and the other ions in alkaline seawater (OIAS) is investigated to understand the activity and stability for nickel foam (NF) electrodes as both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) electrodes. As a whole, the activity of HER electrode is mainly dropped with the increasing concentration of OH-, while the OER electrode is enhanced with the increasing concentration of OH- and Cl-. However, the all (OH-, Cl- and OIAS) increasing ion concentrations decrease the HER electrode stability, while the Cl- reduces, the OH- and OIAS enhances the stability of OER electrode. Moreover, the chloride evolution reaction (ClER) in 6 M NaOH with seawater can be ignored even though the concentration of salts in alkaline seawater reach to saturation. (c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

Studying the changes in electrode activity and stability caused by increasing ion concentration in alkaline seawater electrolysis is essential for industrial-level seawater electrolysis. This study investigates the concentration of hydroxide ion (OH-), chlorine ion (Cl-), and other ions in alkaline seawater (OIAS) to understand the activity and stability of nickel foam (NF) electrodes in hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Overall, the activity of HER electrode decreases with increasing OH- concentration, while the OER electrode is enhanced by increasing OH- and Cl- concentration. However, increasing ion concentrations (OH-, Cl-, and OIAS) decrease the stability of HER electrode, while Cl- reduces the stability and OH- and OIAS enhance the stability of OER electrode. Additionally, the chloride evolution reaction (ClER) in 6 M NaOH with seawater can be ignored despite reaching saturation of salt concentration in alkaline seawater.