Arming Amorphous NiMoO₄ on Nickel Phosphide Enables Highly Stable Alkaline Seawater Oxidation

Seawater electrolysis holds tremendous promise for the generation of green hydrogen (H₂). However, the system of seawater-to-H₂ faces significant hurdles, primarily due to the corrosive effects of chlorine compounds, which can cause severe anodic deterioration. Here, a nickel phosphide nanosheet array with amorphous NiMoO₄ layer on Ni foam (Ni₂P@NiMoO₄/NF) is reported as a highly efficient and stable electrocatalyst for oxygen evolution reaction (OER) in alkaline seawater. Such Ni₂P@NiMoO₄/NF requires overpotentials of just 343 and 370 mV to achieve industrial-level current densities of 500 and 1000 mA cm^-2, respectively, surpassing that of Ni₂P/NF (470 and 555 mV). Furthermore, it maintains consistent electrolysis for over 500 h, a significant improvement compared to that of Ni₂P/NF (120 h) and Ni(OH)₂/NF (65 h). Electrochemical in situ Raman spectroscopy, stability testing, and chloride extraction analysis reveal that is situ formed MoO₄ ^2-/PO₄ ^3- from Ni₂P@NiMoO₄ during the OER test to the electrode surface, thus effectively repelling Cl^- and hindering the formation of harmful ClO^-.