Seawater Electrolysis for Sustainable Hydrogen Production: From Material Design to System Engineering

Seawater electrolysis is an attractive pathway for sustainable green hydrogen production, offering a solution to the global energy transition and avoiding freshwater scarcity. However, the complex ionic composition of seawater fundamentally alters the electrochemical environment, giving rise to chlorine evolution, corrosion, scaling, and membrane degradation, which sharply distinguish it from pure‐water electrolysis. In this review, we present a multiscale perspective on seawater electrolysis that bridges material chemistry, device architecture, and system‐level strategies. We summarize core electrochemical fundamentals, catalyst structure–activity–stability relationships, and assess pure‐water catalyst applicability to seawater. We then critically assess the applicability of idealized‐electrolyte catalysts in seawater, the distinct design requirements of seawater electrolyzers, and the implications for practical operation. Subsequently, recent advances in both indirect and direct seawater electrolysis are compared, with emphasis on their advantages, limitations, and techno‐economic considerations. Finally, we highlight remaining scientific and engineering bottlenecks and outline future directions for durable, selective, and scalable seawater electrolysis.