CeO ₂ -Stabilized Ni ₄ Mo Alloys as Robust Alkaline Hydrogen-Evolving Electrocatalysts for Anion Exchange Membrane Water Electrolysis

The ampere-level alkaline hydrogen evolution reaction (HER) requires catalysts that combine high activity with long-term stability, yet benchmark NiMo alloys suffer from severe Mo leaching during operation. Here, we report a surface passivation strategy using CeO 2 -stabilized Ni 4 Mo alloys on MoO 2 (CeO 2 –Ni 4 Mo/MoO 2 ) for robust alkaline HER. Experimental and theoretical results reveal that surface CeO 2 suppresses hydroxide-induced Mo dissolution while maintaining the reduced state of Ni 4 Mo and promoting interfacial water dissociation, thereby accelerating HER kinetics and increasing stability. Our catalyst delivers 1.0 A cm –2 at an overpotential of 165 mV and sustains hydrogen production for more than 3000 h with negligible decay. When used as the cathode in a platinum-group-metal-free AEM water electrolyzer, it achieves a value of 2.0 A cm –2 at 1.68 V, surpassing the DOE 2026 AEM benchmark of 2.0 A cm –2 at 1.8 V, and operates for 1200 h at 1.0 A cm –2 with a low degradation rate of 42.8 μV h –1 .