Mitigating Cl−-induced detrimental effects to enhance seawater electrolysis

Abstract

Direct seawater electrolysis (DSE) represents a sustainable pathway for green hydrogen production by leveraging abundant seawater resources and offshore renewable energy. However, chloride ions (Cl⁻), the most abundant dissolved anions in seawater, introduce critical challenges, including corrosion at the anode, competitive chloride oxidation reactions (ClOR), and cathode degradation under reverse current conditions, collectively compromising the efficiency and stability of the electrolysis process. A substantial body of feasible mitigation strategies has already been reported, thereby underscoring the need for a systematic synthesis to further stimulate progress in this research domain. In this review, we first summarize the hazards caused by Cl⁻ in direct seawater electrolysis and the underlying mechanisms, including electrode corrosion, the competition between the ClOR and oxygen evolution, and cathodic damage under reverse or transient conditions. Subsequently, we categorize and synthesize mitigation strategies within a goal-oriented framework: Cl⁻ isolation and shielding, suppression of the ClOR under low-potential operation, chloride valorization and establishment of chloride-free environments. Following this, we discuss the trend toward integrated, hybrid strategies that combine physical shielding, site-affinity tuning, and system-level design to achieve synergistic protection, and we highlight emerging approaches that transform Cl⁻ from a corrosive liability into a functional asset. Last but not least, we offer recommendations and an outlook, identifying key research priorities, challenges related to long-term stability and scale-up, and potential translational pathways to accelerate performance improvements and facilitate the industrial deployment of DSE.