The practical conversion of seawater to hydrogen faces critical limitations from chloride attack and anodic competition, requiring electrocatalysts with superior robustness. Herein, we constructed an amorphous/crystalline heterointerface catalyst, NiO/CoFe Prussian blue analogues, via low-temperature atomic layer deposition (ALD) toward efficient seawater oxidation. Experimental investigations revealed that utilization of the conformal coating capability of ALD enabled precise integration of a structurally disordered NiO layer onto the crystalline CoFe-PBA framework. This integration resulted in the formation of a robust heterointerface, which synergized the amorphous phase's isotropic corrosion resistance and the crystalline matrix's high conductivity. The catalyst achieved overpotentials of η₁₀ = 257 mV and η₁₀₀ = 301 mV in alkaline seawater. Computational analysis demonstrated that the oxygen-bridged Fe/Co–O–Ni covalent interactions induced strong electronic coupling, modulating the 3d orbital configuration of Fe/Co/Ni sites. This, in turn, led to a downshifted d-band center, optimizing oxygen intermediate adsorption and enhancing the chloride tolerance via Co sites. Notably, 100 hour stability at 100 mA cm⁻² was maintained. This work introduces an ALD-enabled interfacial engineering methodology for fabricating durable heterointerface catalysts tailored for seawater electrolysis hydrogen production.

Modulating the local electronic state of metal compounds through interfacial interaction has become a key method for manufacturing high‐performance hydrogen evolution reaction (HER) electrocatalysts. The electron‐rich active sites can promote the adsorption of hydrogen, which accelerates the Volmer step and thereby enhances the electrocatalytic performance of HER. Here, we found that the strong interfacial interaction between TiO nanodots (TiO/Co−S) and Co−S nanosheets could advantageously improve the performance toward HER of electrocatalyst. Meanwhile, XPS results showed that modulating the local electronic structure of the TiO nanodots produces electron‐rich regions on Co. As a result, the overpotential of the TiO/Co−S nanocomposite at 10 mA cm⁻² was 107 mV, and the Tafel slope was 83.3 mV dec⁻¹. This study focused on the effect of the solid‐solid interface on the local electronic structure of the catalytic metal active sites and successfully improved the catalytic activity of transition metal materials in HER catalysis.