image: Designed strategies in upgrading chloride to chlorine in seawater, including electrolyte optimization, electrolyte design, direct adsorption of Cl- and transition of active sites.
Credit: ©Science China Press
Seawater has long perceived as an attractive, abundant, and low-cost feedstock for electrochemical energy conversion and valuable chemical synthesis. However, seawater holds a diverse range of monovalent and multivalent ions (e.g. Na+, K+, Mg2+, Ca2+, Cl-, Br-, SO42-, etc) which pose significant operational challenges, such as competing side reactions, precipitates production and corrosion. This work demonstrates, rather than being obstacles, many of the ions can be utilized intentionally to improve electrochemical performance and mitigate their detrimental effect if they are properly integrated into system design.
The authors first summarise the stat-of-the-art seawater electrocatalysis, identifying the key issues associated with multicomponent environments. They elucidate how specific ions affect electrocatalytic performance. A key focus is an in-depth look at methodologies for utilizing chloride ion (Cl-) in various electrochemical reactions, alongside intelligent protocols for sodium ion (Na+) harness, including asymmetric cell design and aqueous alternating strategies. Furthermore, Mg2+ and Ca2+ can influence local pH and ion transport, thus, local pH limitation and additional force-repelling approaches introduce a platform for co-synthesis of hydrogen and value-added Mg(OH)2 in direct seawater electrocatalysis. Finally, the smart electrochemical methods for the extraction of valuable resources like uranium and lithium from seawater are summarised, with a focus on innovative electrode modifications and optimal cell configurations.
The study shows that thoughtfully designed catalyst and electrolyte adjustment strategies can turn these ions from hindrances into functional assets. Material-design approaches receive detailed attention, such as tailoring advanced materials that enable special ion-adsorption behaviour; engineering catalyst supports or membrane that modulate ion-flux; and coupling electrocatalysis with ion-exchange or ion-separation steps. In this review, authors highlight case studies where utilizing ion effect leads to enhanced stability, selectivity, or efficiency for seawater electrolysis.
Finally, the authors outline a forward-looking agenda for the field, elucidating underexplored ion-catalyst interaction mechanism, real-world system integration, and scalable engineering challenges. They emphasize a fundamental shift: from suppressing the adverse effects of ions to harnessing them, paving a sustainable, cost-effective seawater electrocatalysis and other electrocatalytic transformations. This work offers researchers working in catalysis, materials science, and electrochemistry a vital roadmap in this emerging field of ‘ion-utilized’ seawater electrocatalysis.