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

ABSTRACT Seawater electrolysis for production of brucite minerals and green H 2 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 H 2 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 H 2 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 H 2 . 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 H 2 generation with value‐added mineral production, addressing the fundamental trade‐off between gas evolution and mineralization in scalable marine resource utilization.