Regulating Interfacial H ₂ O Activity and H ₂ Bubbles by Core/Shell Nanoarrays for 800 h Stable Alkaline Seawater Electrolysis

Abstract The catalytic activity and stability under high current densities for hydrogen evolution reactions (HER) are impeded by firm adherence and coverage of H ₂ bubbles to the catalytic sites. Herein, we systematically synthesize core/shell nanoarrays to engineer bubble transport channels, which further remarkably regulate interfacial H ₂ O activity, and swift H ₂ bubble generation and release. The self‐supported catalyst holds uniform ultra‐low Ru active sites of 0.38 wt% and promotes the rapid formation of plentiful small H ₂ bubbles, which are rapidly released by the upright channels, mitigating the blockage of active sites and avoiding surface damage from bubble movements. As a result, these core/shell nanoarrays achieve ultralow overpotentials of 18 and 24 mV to reach 10 mA cm ⁻² for HER in 1 M KOH freshwater and seawater, respectively. Additionally, the assembled electrolyzer demonstrates stable durability over 800 hours with a high current density of 2 A cm ⁻² in 1 M KOH seawater. The techno‐economic analysis (TEA) indicates that the unit cost of the hydrogen production system is nearly half of the DOE's (Department of Energy) 2026 target. Our work addresses the stability challenges of HER and highlights its potential as a sustainable and economically feasible solution for large‐scale hydrogen production of seawater.