In Situ Engineering a Dual-Anion Rejection Interface for High-Efficiency Oxygen Evolution in Alkaline Seawater

Seawater electrolysis is pivotal for sustainable hydrogen production, yet chloride-induced catalyst corrosion severely hinders its efficiency. Here, a (Mo, Co)P x electrocatalyst via a two-step hydrothermal-phosphorization strategy is engineered, enabling in situ formation of a dynamic dual-anion (MoO 4 2 ⁻/PO 4 3 ⁻) Cl − -rejection interface. This tailored interface effectively blocks Cl − adsorption while preserving hydroxyl accessibility, significantly enhancing corrosion resistance in alkaline seawater. The optimized (Mo, Co)P x delivers exceptional oxygen evolution reaction performance in alkaline seawater electrolysis, achieving ultralow overpotentials of 213 and 360 mV to reach current densities of 10 and 1000 mA cm −2 , respectively. Remarkably, the (Mo, Co)P x with an in situ-generated dual-anion rejection layer demonstrates exceptional durability, exhibiting only a 20mV performance degradation during a 480-h stability test under high-current conditions. In situ Raman spectroscopy, in situ attenuated total reflectance surface-enhanced infrared absorption spectroscopy, and density functional theory calculations demonstrate that the dual-anion layer not only enhances Cl − rejection but also promotes rapid surface reconstruction of Co species and enhances interfacial water adsorption, thereby suppressing the competitive chlorine evolution reactions. This work provides a rational strategy for designing durable electrocatalysts with in situ-engineered anion-rejection interfaces, advancing efficient alkaline seawater electrolysis.