Anion-shielded interfaces: Borate-etched CoFe LDH unlock stable seawater splitting

Developing chloride-tolerant electrocatalysts for seawater splitting remains challenging due to severe anode corrosion and competing chlorine evolution reaction (CER). Here, we propose a boric acid etching strategy to transform CoFe layered double hydroxide (LDH) into BO 3 3- -modified CoFeB catalysts, which simultaneously achieve exceptional oxygen evolution reaction (OER) activity (247.4 mV @ 100 mA cm −2 ) and corrosion resistance in alkaline seawater. The interfacial BO 3 3− species suppress chloride adsorption while promoting generation of highly active Co 3+ sites, as theoretically verified by density functional theory calculations showing preferential OH − adsorption and optimized OOH∗ intermediate binding. When integrated in membrane-free electrolyzers (Pt/C || CoFeB), the system delivers ultralow voltages (1.847 V@500 mA cm −2 ) with satisfactory stability (150 h@500 mA cm −2 ), significantly outperforming commercial RuO 2 counterparts. This work establishes an anion-engineering paradigm through controlled etching, offering a cost-effective scalable solution for industrial hydrogen production from seawater. • BO 3 3− solving corrosion and boosting activity simultaneously. • Controlled etching engineering on CoFe LDH with attached anions. • CoFeB shows superior OER performance and selectivity in natural seawater.