Interfacial Hydration Engineering Synchronizes Hydrogen Evolution and Brucite Mineralization in Seawater Electrolysis

Seawater electrolysis for production of brucite minerals and green H₂ encounters critical interfacial challenges under high-current operation. Competing gas evolution and magnesium crystallization lead to bubble accumulation and heterogeneous precipitation at the interface, occluding active sites and compromising stability. Here, we develop a nanostructured hydrogen-bonded assembly that decouples H₂ evolution from brucite mineralization through interfacial hydration control. In the assembly, a cobalt phosphide catalyst combined with superaerophobic copolymer matrix creates hydration-repulsive interfaces where ordered water networks expel H₂ bubbles and precipitate brucite evenly. This synergy sustains stable seawater electrolysis at 1000 mA cm^-2 for over 1000 h with stoichiometric co-production efficiency for both brucite and H₂. Extending to photoelectrocatalysis, a perylene diimide-integrated variant achieves 4.5 mA cm^-2 photocurrent and 9.9% quantum efficiency for seawater photoelectrocatalysis. By interfacial hydration engineering, this work establishes a platform that synergizes H₂ generation with value-added mineral production, addressing the fundamental trade-off between gas evolution and mineralization in scalable marine resource utilization.