Modulating Selectivity and Stability of the Direct Seawater Electrolysis for Sustainable Green Hydrogen Production

Direct seawater electrolysis (DSE) has emerged as a compelling route to sustainable hydrogen production, leveraging the vast global reserves of seawater. However, the inherently complex composition of seawater—laden with halide ions, multivalent cations (Mg2+, Ca2+), and organic/biological impurities—presents formidable challenges in maintaining both selectivity and durability. Chief among these obstacles is mitigating chloride corrosion and suppressing chlorine evolution reaction (ClER) at the anode, while also preventing the precipitation of magnesium and calcium hydroxides at the cathode. This review consolidates recent advances in material engineering and cell design strategies aimed at controlling undesired side reactions, enhancing electrode stability, and maximizing energy efficiency in DSE. We first outline the fundamental thermodynamic and kinetic hurdles introduced by Cl⁻ and other impurities. This discussion highlights how these factors accelerate catalyst degradation and drive suboptimal reaction pathways. We then delve into innovative approaches to improve selectivity and durability of DSE—such as engineering protective barrier layers, tuning electrolyte interfaces, developing corrosion-resistant materials, and techniques to minimize Mg/Ca-related precipitations. Finally, we explore emerging reactor configurations, including asymmetric and membrane-free electrolyzers, which address some barriers for DSE commercialization. Collectively, these insights provide a framework for designing next-generation DSE systems, which can achieve large-scale, cost-effective, and environmentally benign hydrogen production.