Durable Alkaline Seawater Oxidation over Hierarchical NiNH@NiFe LDH Nanoarrays

Seawater electrolysis is promising for renewable hydrogen production. However, the high concentration of chloride ions (Cl^-) and their derivatives (HClO/ClO^-) in seawater cause severe corrosion of the anode catalyst, posing a major challenge to the stability of the seawater electrolysis. Herein, we present the development of NiFe-layered double hydroxide nanosheets on nickel nitrate hydroxide nanoarrays supported on nickel foam. As a 3D catalyst electrode for alkaline seawater oxidation (ASO), such a hierarchical nanoarray (NiNH@NiFe LDH/NF) requires a low overpotential of 323 mV to obtain a current density of 1000 mA cm^-2 and operates stably for 800 h at the same current density. In situ Raman spectroscopy analysis indicates that NiNH@NiFe LDH/NF releases nitrate ions that adsorb on the catalyst surface during the ASO process, favoring electrostatic repulsion to Cl^- and enhancing the corrosion resistance of the catalyst. Furthermore, the two-electrode electrolyzer using NiNH@NiFe LDH/NF as the anode and Pt/C/NF as the cathode needs only 2.27 V to attain 500 mA cm^-2 and maintains stable electrolysis for 460 h, highlighting its exceptional durability for practical seawater electrolysis applications.