From a Foe to a Friend: Harnessing Chloride Ions to Stabilize RuO ₂ Electrocatalysts for the Oxygen Evolution Reaction in Alkaline Seawater Electrolysis

A large amount of research on electrolysis has mainly focused on pure water systems under different pH conditions. However, the scarcity of freshwater resources has led to an increasing interest in electrolysis studies using seawater. During the electrolytic process, chloride ions (Cl–) present in seawater participate in a chlorine evolution reaction (CER), resulting in the corrosion and deterioration of both electrodes and electrocatalysts. Most researchers consider Cl– to be highly detrimental during the electrolysis process and have explored various methods to mitigate its negative effects. In this study, we found that the presence of Cl– enhanced the anchoring of RuO2 when using RuO2/WO3/carbon cloth (CC) electrocatalysts for the oxygen evolution reaction (OER) in alkaline simulated seawater (1.0 M KOH + 0.5 M NaCl). RuO2/WO3/CC inherited the excellent chloride corrosion resistance of WO3 and demonstrated outstanding OER stability for 230 h at a current density of 10 mA cm–2 in 1.0 M KOH + 0.5 M NaCl electrolyte. In contrast, in the absence of Cl–, after conducting OER stability tests with RuO2/WO3/CC in an alkaline solution (1.0 M KOH), RuO2 was more prone to dissolve into the electrolyte, leading to a degradation in catalytic performance. Overall, this work transforms the perception of Cl– from an enemy to an ally in electrolytic oxygen production, challenging the prevailing negative bias and opening new pathways for efficient seawater electrolysis.