Synergistic Chloride Repulsion in Hierarchical NiFe LDH/Co(OH)₂ Heterostructure Enables Industrial-Grade Current Density and Ultra-stability for Seawater Electrolysis over 4600 h

The development of efficient and robust oxygen evolution reaction (OER) catalysts is crucial for practical seawater electrolysis. This work presents a hierarchical heterostructure achieved by epitaxially growing NiFe layered double hydroxide (LDH) nanosheets on Co(OH)₂ nanorod arrays. During the OER process, this precatalyst undergoes in situ surface transformation into the active phases, NiFeOOH and CoOOH. It is at this in situ formed heterointerface that a dual-defense mechanism against chloride corrosion is established: (1) the built-in electric field induces electron enrichment in the NiFeOOH phase, creating an electrostatic shield to repel Cl^–; (2) the high-spin Co³⁺ sites in CoOOH strongly adsorb Cl^–, forming a dense Co–Cl layer that acts as a physical barrier. This synergy effectively protects the active sites, enabling the catalyst to deliver exceptional performance in alkaline seawater, with a low overpotential of 358 mV at 500 mA cm^–2 and remarkable stability maintained for over 4600 h. In a real seawater AEM electrolyzer, this catalyst-based electrode requires only 2.34 V to reach 6 A cm^–2 and simultaneously demonstrates stable operation for over 250 h at 1 A cm^–2. This study underscores the importance of designing dynamic interfaces for creating highly durable electrocatalysts for sustainable hydrogen production. © 2026 American Chemical Society.