Design of asymmetric electronic spring for stabilizing selective seawater oxidation

ABSTRACT 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.