A highly efficient electrocatalyst for direct seawater oxidation is developed, featuring an amorphous molybdenum oxide (MoO₃) layer on a beaded-like cobalt oxide (CoO) interface, constructed via atomic layer deposition (ALD). This catalyst achieves long-term stability (>1000 h) at 600 mA/cm² with a Faraday efficiency of 100%. The MoO₃ layer inhibits anodic oxygen evolution reaction (OER) and selective chlorine evolution reaction (CER) by shielding Cl⁻ and enabling dynamic surface self-reconstruction. The catalyst, MoO₃@CoO/CC, demonstrates high selectivity and stability in seawater electrolysis, producing hydrogen at 419.4 mL/cm²/h with a power consumption of 4.62 kWh/m³ H₂, lower than that of pure water. The catalyst maintains high performance under various conditions, including high salinity and real seawater, with a current density of 600 mA/cm² at 1.70 V in 6 M KOH + 1.5 M NaCl. The MoO₃ layer also enhances OER kinetics by regulating the interface and preventing deep reconstruction, leading to a low overpotential and high efficiency. The catalyst is integrated into a two-electrode flow cell, achieving 1 A/cm² at 1.93 V for 500 h with a Faraday efficiency of 95%. This study provides a promising solution for efficient and economical hydrogen production via direct seawater electrolysis.A highly efficient electrocatalyst for direct seawater oxidation is developed, featuring an amorphous molybdenum oxide (MoO₃) layer on a beaded-like cobalt oxide (CoO) interface, constructed via atomic layer deposition (ALD). This catalyst achieves long-term stability (>1000 h) at 600 mA/cm² with a Faraday efficiency of 100%. The MoO₃ layer inhibits anodic oxygen evolution reaction (OER) and selective chlorine evolution reaction (CER) by shielding Cl⁻ and enabling dynamic surface self-reconstruction. The catalyst, MoO₃@CoO/CC, demonstrates high selectivity and stability in seawater electrolysis, producing hydrogen at 419.4 mL/cm²/h with a power consumption of 4.62 kWh/m³ H₂, lower than that of pure water. The catalyst maintains high performance under various conditions, including high salinity and real seawater, with a current density of 600 mA/cm² at 1.70 V in 6 M KOH + 1.5 M NaCl. The MoO₃ layer also enhances OER kinetics by regulating the interface and preventing deep reconstruction, leading to a low overpotential and high efficiency. The catalyst is integrated into a two-electrode flow cell, achieving 1 A/cm² at 1.93 V for 500 h with a Faraday efficiency of 95%. This study provides a promising solution for efficient and economical hydrogen production via direct seawater electrolysis.