Fluoride-Engineered Electrolyte for Highly Stable and Efficient Alkaline Seawater Electrolysis at 2 A cm−2

Abstract

Seawater electrolysis offers an energy-efficient route for hydrogen production while alleviating freshwater scarcity. However, the presence of Cl− in seawater compromises anode activity and induces severe corrosion, requiring constructing complex electrode architectures that hinder large-scale application. In this work, we demonstrate that incorporating F− as an electrolyte additive significantly enhances the performance of NiFe layered double hydroxide (NiFe-LDH) anodes. Upon optimizing the F− concentration, benchmark NiFe-LDH showed the lower overpotential than that of the F−-free system, and achieved stable operation at 2 A cm−2 for 1000 h in seawater electrolyte, representing an approximately 500-fold improvement over the control set of experiment. The consistency between spectroscopic characterization and multi-scale simulation results revealed that F−, by virtue of its high electronegativity and charge density, modulates the electronic environment of Ni and Fe sites, enhances the adsorption of OH−, and thereby improves OER activity. Moreover, the introduction of F− increases free water content and modulates the hydrogen bond network to promote OH− transportation while repelling Cl− at the electrode-electrolyte interface by polarizing the O─H bonds of water molecules on NiFe-LDH surface. This straightforward electrolyte engineering strategy provides a practical and scalable solution for seawater electrolysis.