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

Abstract Seawater electrolysis holds tremendous promise for the generation of green hydrogen (H 2 ). However, the system of seawater‐to‐H 2 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 NiMoO 4 layer on Ni foam (Ni 2 P@NiMoO 4 /NF) is reported as a highly efficient and stable electrocatalyst for oxygen evolution reaction (OER) in alkaline seawater. Such Ni 2 P@NiMoO 4 /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 Ni 2 P/NF (470 and 555 mV). Furthermore, it maintains consistent electrolysis for over 500 h, a significant improvement compared to that of Ni 2 P/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 MoO 4 2− /PO 4 3− from Ni 2 P@NiMoO 4 during the OER test to the electrode surface, thus effectively repelling Cl − and hindering the formation of harmful ClO − .