Laser-Induced NiFeO_x Nanolayer Enables Durable and Efficient Seawater Electrolysis at Industrial Current Densities

Seawater electrolysis is an emerging pathway for sustainable hydrogen production, yet long-term operation under industrial current densities is severely constrained by chloride-induced corrosion and catalyst degradation. Here, we introduce a laser-induced interface engineering strategy that leverages the rapid thermal dynamics of laser powder bed fusion (LPBF) to construct a ∼5 nm nonstoichiometric NiFeO_x nanolayer epitaxially grown to a NiFe alloy substrate. This in situ fabricated nanolayer functions as a multifunctional interface, selectively adsorbing OH^- ions through stable metal-oxygen (M-O) bonding, thereby suppressing Cl^--driven surface degradation while simultaneously accelerating the oxygen evolution reaction (OER) kinetics by lowering the Gibbs free energy barrier of the OER intermediates (*OH) from 0.61 to 0.48 eV. As a result, the NiFe with oxide layer (NiFe-OL) electrode achieves an overpotential of 238 mV at 10 mA cm^-2 in simulated seawater, showing a marked 84 mV reduction compared to the bare NiFe alloy electrode, and maintains stable operation for over 1000 h at 1 A cm^-2 in alkaline seawater. This represents more than 25 times longer operational stability than the bare NiFe electrode, which fails after only ∼20 h under identical conditions. In particular, the laser-formed functionally integrated oxide nanointerface delivers a distinctive combination of corrosion resistance and electrochemical kinetics. Our findings demonstrate a robust seawater electrolysis electrode and demonstrate the applicability of scalable interface engineering for application in corrosive electrochemical systems.