Built-In Electric Fields and Ir-Cl Motifs at Heterointerfaces Enable Selective and Durable Seawater Electrolysis

Abstract

Alkaline seawater electrolysis is fundamentally constrained by intrinsic trade-offs among oxygen evolution reaction (OER) activity, selectivity, and durability, arising from sluggish OER kinetics, parasitic chloride oxidation, and catalyst degradation. Here, we report an integrated interfacial design of an Ir/NiFe layered double hydroxide (Ir/NiFe LDH) heterostructure that unifies dual-pathway OER kinetic promotion with a chloride-sink effect at a heterointerface. Spontaneous interfacial charge transfer from metallic Ir to NiFe LDH establishes a built-in electric field, which regulates electronic structure of the Ni/Fe active centers and simultaneously activates both the adsorbate evolution mechanism and the lattice oxygen mechanism, thereby accelerating OER kinetics. Meanwhile, the coupled Ir domains serve as robust chloride sinks: Cl- preferentially coordinates to Ir sites to form stable Ir-Cl motifs, redirecting corrosive chloride species away from the NiFe OER active centers and suppressing chloride oxidation side reactions. Consequently, the catalyst delivers an ultralow overpotential of 201 mV at 10 mA cm-2 in alkaline natural seawater and sustains operation for over 5200 h at 500 mA cm-2 in a commercial electrolyzer with negligible voltage decay, achieving an energy efficiency of 71.2% and an electricity cost of US$0.944 kg-1 H2. This work resolves the long-standing activity-selectivity-durability trade-off in alkaline seawater electrolysis and provides a general interfacial engineering strategy for high-performance electrocatalysis in chemically competitive complex electrolytes.