Heterogeneous Structure of Ni–Mo Nanoalloys Decorated on MoO_x for an Efficient Hydrogen Evolution Reaction Using Hydrogen Spillover

Herein, a heterogeneous structure of Ni-Mo catalyst comprising Ni₄Mo nanoalloys decorated on a MoO_x matrix via electrodeposition is introduced. This catalyst exhibits remarkable hydrogen evolution reaction (HER) activity across a range of pH conditions. The heterogeneous Ni-Mo catalyst showed low overpotentials only of 24 and 86, 21 and 60, and 37 and 168 mV to produce a current density of 10 and 100 mA cm^-2 (η₁₀ and η₁₀₀) in alkaline, acidic, and neutral media, respectively, which represents one of the most active catalysts for the HER. The enhanced activity is attributed to the hydrogen spillover effect, where hydrogen atoms migrate between the Ni₄Mo alloys and the MoO_x matrix, forming hydrogen molybdenum bronze as additional active sites. Additionally, the Ni₄Mo facilitated the water dissociation process, which helps the Volmer step in the alkaline/neutral HER. Through electrochemical analysis, in situ Raman spectroscopy, and density functional theory calculations, the fast HER mechanism is elucidated.