Hexafluoroantimonate-intercalated NiFe layered double hydroxide enables stable alkaline seawater oxidation at ampere-level current densities

Abstract

Renewable electricity-driven seawater electrolysis for hydrogen production offers substantial potential for sustainable energy solutions. However, the high concentration of chloride ions (Cl⁻) in seawater triggers competitive chemical reactions and severe corrosion, posing a challenge to the durability of the anode. In this study, we present a hexafluoroantimonate-intercalated NiFe layered double hydroxide nanosheet array on Ni foam (SbF₆⁻-NiFe LDH/NF), which serves as a highly active and stable electrocatalyst for alkaline seawater oxidation (ASO). SbF₆⁻-NiFe LDH/NF requires only an overpotential of 379 mV to achieve a current density of 1000 mA cm⁻², significantly outperforming NiFe LDH/NF (396 mV). Furthermore, it exhibits excellent long-term stability over 600 hours at 1000 mA cm⁻², with only trace amounts of active chlorine detected during the ASO process. In situ Raman spectroscopy confirms that the insertion of SbF₆⁻ into the LDH layers promotes the formation of active sites. More importantly, SbF₆⁻ efficiently repels Cl⁻, thus providing robust protection to the anode. This development represents a significant advancement in the design of noble-metal-free, durable anode electrodes for ASO.