Reshaping Chloride Exclusion in Stern Layer to Enable Durable Seawater Electrolysis

ABSTRACT Direct seawater electrolysis offers a promising route for green hydrogen by utilizing marine resources and offshore renewables, but is hindered by chloride‐induced corrosion and poor catalyst durability. Herein, the Helmholtz plane microenvironment is reshaped by in situ MoO 4 2− release from a nickel‑molybdate precursor (Ni 0.36 Mo 0.64 ‐OH). The anions enrich within the Stern layer, forming a high‐concentration gradient of an anionic layer that electrostatically repels Cl − and prevents chloride‐corroded side reactions. Unlike the conventional strategy of bulk anion addition, this in situ self‐delivery approach bypasses long‐range diffusion and breaks mass‐transfer limitation, enabling rapid anion shielding via short‐range interfacial transport. Concurrently, the leaching of MoO 4 2− induces surface electronic redistribution that enhances Ni─O bond covalency, thereby triggering the lattice oxygen mechanism (LOM) for the oxygen evolution reaction (OER) while partially retaining the adsorbate evolution mechanism (AEM). The coexistence of two pathways ensures AEM‐induced structural stability and simultaneously enhances LOM‐dominated intrinsic activity. Consequently, the activated catalyst (A‐Ni 0.36 Mo 0.64 ‐OH) achieves low overpotentials (201 mV@10 mA cm −2 ; 560 mV@2 A cm −2 ) and long‑term stability (3500 h@250 mA cm −2 ) with negligible chlorine corrosion in alkaline seawater. This work presents an interfacial design that concurrently resists chloride corrosion and enhances OER activity by manipulating both ionic and electronic environments.