Surface borate layer dramatically enhances the stability of NiFe-layered double hydroxide for alkaline seawater oxidation

Seawater electrolysis presents a sustainable approach for producing green hydrogen using renewable energy sources. However, chloride ions (Cl ) and their derivatives significantly reduce the durability of anode catalysts, severely hindering their practical application. In this work, we developed a borate (Bi) modified NiFe layered double hydroxide on nickel foam (NiFe LDH@NiFe-Bi/NF) to blocks Cl and mitigates chlorine reactions during alkaline seawater oxidation (ASO). In situ electrochemical spectroscopic studies show that the Bi layer effectively promotes NiOOH formation, thereby enhancing oxygen evolution reaction (OER) activity. Specifically, the B4O72 -rich anionic overlayer effectively prevents Cl adsorption and thus protect the active site during ASO. As a result, NiFe LDH@NiFe-Bi/NF requires a lower overpotential (eta) of 354 mV to achieve an industrial current density (j) of 1000 mA cm 2 compared to NiFe LDH/NF, which requires 407 mV, in a 1 M KOH + seawater. Notably, NiFe LDH@NiFe-Bi/NF exhibits exceptional long-term electrochemical durability, maintaining stable operation for 600 h at a j of 1000 mA cm 2 in alkaline seawater. Additionally, membrane electrode assembly fabricated with NiFe LDH@NiFe-Bi/NF requires lower eta to reach the same voltages than Pt/C/NF||RuO2/NF. Furthermore, Pt/C/NF||NiFe LDH@NiFe-Bi/NF operates at 300 mA cm 2 for 150 h without significant activity degradation.