Spatially Decoupled Active and Sacrificial Sites in Titanium Oxide Nanosheets Promote Durable Natural Seawater Electrolysis

Direct seawater electrolysis offers a promising route for scalable green hydrogen production, yet its practical implementation is hindered by sluggish reaction kinetics, parasitic side reactions, and catalyst degradation under harsh saline conditions. To address these challenges, we engineered a single-atom copper-doped titanium oxide (Cu₁-TiO₂) nanosheet catalyst featuring spatially decoupled asymmetric Cu-Ti atomic pairs and Ti vacancies. The asymmetric Cu-Ti pairs, serving as active sites, optimize the rate-determining water dissociation step while enabling sequential hydrogen desorption during the hydrogen evolution reaction (HER), significantly accelerating reaction kinetics. Concurrently, the Ti vacancies serve as sacrificial sites, preferentially confining cations from seawater via electrodeposition. This self-sacrificing mechanism preserves fouling of the Cu-Ti active sites, ensuring long-term stability of the integrity. The spatial and functional decoupling of active and sacrificial sites endows the Cu₁-TiO₂ catalyst with a remarkably low overpotential of 160 mV at 10 mA cm^-2 and exceptional durability in natural seawater, outperforming commercial Pt/C. A method integrating Cu₁-TiO₂ cathodes with NiFe hydroxide anodes demonstrates superior efficiency and cost-effectiveness. This study provides a strategic approach to designing catalysts with spatially decoupled active and sacrificial sites, offering a pathway to advance both activity and durability in complex environments.