Ni–P Nanoarray Scaffolds That Elevate Self‐Supported Phosphides and Commercial Catalysts for Alkaline and Anion‐Exchange‐Membrane Water Electrolysis

ABSTRACT Alkaline water electrolysis offers a cost‐effective and robust route to green hydrogen production, but its practical deployment is hindered by sluggish hydrogen evolution reaction (HER) kinetics and electrode degradation. Herein, we report a self‐supported hierarchical Co ₃ Mo ₁ ‐P/Ni‐P/NF (NF: nickel foam) electrode fabricated by a two‐step molten‐salt method. Vertically aligned Ni‐P nanoneedles are grown directly on NF, followed by deposition of a Co ₃ Mo ₁ ‐P catalytic overlayer. The resulting electrode requires only 45.9 mV at 10 mA cm ⁻² and delivers outstanding high‐current alkaline HER performance, outperforming previously reported transition‐metal phosphide electrodes. This activity arises from synergistic Co‐Mo chemistry, beneficial Ni‐P/catalyst interfacial effects, and engineered surface topography that accelerates bubble release while maximizing active‐site exposure. The Ni‐P scaffold further enhances physical and chemical robustness, enabling stable water splitting for 200 h. Moreover, integrating commercial Pt/C with the Ni‐P nanoarray increases the electrochemically active surface area by 4.52‐fold and achieves 55.8 mV at 100 mA cm ⁻² , demonstrating the versatility of the scaffold. Single‐cell anion‐exchange membrane water electrolysis (AEMWE) further confirms that this hierarchical phosphide architecture translates intrinsic catalytic advantages into superior cell‐level performance under practical membrane‐electrode assembly conditions.