Design of asymmetric electronic spring for stabilizing selective seawater oxidation

The core in direct seawater electrolysis lies in developing efficient and corrosion-resistant electrocatalysts to suppress detrimental chloride oxidation reaction. This work introduces an anodic electrocatalyst interface modulation strategy, revealing that NiFeOOH modified with Cr₂O₃ forms flexible Cr-O-Ni asymmetric bonds, which function as a dynamic 'electronic spring' during the oxygen-evolution reaction (OER). The introduction of Cr₂O₃ selectively converts NiFeOOH into the active β phase. Under high potentials, the dynamic Cr-O-Ni electronic modulation prevents the overoxidation of Ni active sites, stabilizing them in the highly active +3 oxidation state, and simultaneously promotes the transformation from the adsorbate evolution mechanism (AEM) to the lattice oxygen oxidation mechanism. In alkaline seawater, high-valence Cr acts as a Lewis acid to enhance OH^- adsorption while its electrostatic repulsion suppresses Cl^- accumulation, significantly boosting OER activity and selectivity. Remarkably, the as-synthesized Cr₂O₃-NiFeOOH delivers 1.0 A cm^-2 at just 1.60 V in alkaline seawater, maintaining exceptional stability for over 500 h, and can even maintain high stability at 500 mA cm^-2 when deployed in an AEM electrolyser. The Cr₂O₃-NiFeOOH anode also achieves 77.9% energy efficiency at 100 mA cm^-2, producing hydrogen at $0.85 per gasoline gallon equivalent, demonstrating industrial viability for seawater electrolysis.