High-entropy alloys as emerging electrocatalysts for seawater electrolysis

Direct seawater electrolysis could enable green hydrogen production without competing for scarce freshwater resources, but its practical use is limited by chloride oxidation, catalyst corrosion, scaling, impurity deposition and long-term electrolyser instability. High-entropy alloys and related high-entropy-derived catalysts provide a versatile platform for addressing these coupled challenges because their multimetallic active sites, lattice distortion, defect-rich surfaces and adaptive reconstruction can be tuned to regulate hydrogen and oxygen evolution while limiting chlorine evolution and chloride-driven degradation. This Review examines recent progress in high-entropy alloy, oxide, hydroxide, phosphide, sulfide and related electrocatalysts for seawater splitting, with emphasis on activity-selectivity-stability relationships rather than activity alone. We discuss how composition, surface reconstruction, defect chemistry, electronic modulation and electrolyte engineering influence HER and OER kinetics, chlorine suppression and corrosion resistance in model saline electrolytes and real seawater. We also highlight the need for realistic benchmarking, including high-current operation, long-term durability, direct chlorine/hypochlorite quantification, operando identification of reconstructed active phases, and scalable synthesis. The Review concludes by outlining how mechanistically informed catalyst design, robust electrolyser architectures and standardised seawater testing can move high-entropy electrocatalysts closer to practical hydrogen production.