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.