In this work, ternary Mo–Ni–X (X = Al, Co, Cr, Cu, Fe, W) thin films with nominal composition Mo₈₀Ni₁₀X₁₀ (at. %) were prepared by magnetron sputtering and evaluated as electrocatalysts for the hydrogen evolution reaction (HER) in alkaline media. The influence of alloy composition, substrate type, and deposition temperature on catalytic performance was systematically investigated. Electrochemical screening revealed a strong dependence of HER activity on both substrate conductivity and ternary alloying, with Al-, Cr-, and W-containing systems showing the best performance on glassy carbon substrates. This highlights the importance of interfacial charge-transfer efficiency in determining catalytic behavior. The Mo₈₀Ni₁₀Cr₁₀/GC system was selected for detailed analysis. Deposition temperatures ≥ 500 °C resulted in enhanced HER activity, reaching an overpotential of η₁₀ = −222 mV at j = −10 mA cm⁻². The improved performance is attributed to temperature-induced microstructural optimization and electrochemically driven surface reconstruction, leading to the formation of a Ni-enriched active interface. AFM analysis confirmed surface restructuring during operation, with roughness increasing from ~1 to ~3 nm, indicating the formation of additional electrochemically accessible active sites. XPS results suggest partial depletion of Mo during cycling, while Cr mainly contributes to structural stabilization of the evolving thin film. Overall, the results demonstrate that HER performance is governed by the coupled effects of alloy composition, substrate-dependent charge transport, and in situ surface reconstruction. This work highlights magnetron sputtering as a scalable approach for designing homogeneous noble-metal-free thin-film electrocatalysts with tunable activity.

Understanding the relationship between alloy composition, surface chemistry, and catalytic performance is essential for the rational design of efficient platinum-group-metal-free electrocatalysts for the hydrogen evolution reaction (HER). In this work, 30 nm Mo₈₀Ni₅Al₁₅ thin films were deposited by magnetron sputtering onto five technologically relevant substrates (glassy carbon, highly oriented pyrolytic graphite, graphite, Ni foil, and Ni mesh) to investigate the influence of substrate selection on HER activity and stability in 1 M NaOH. Pure Ni thin films prepared under identical conditions served as reference catalysts. Among the investigated substrates, Ni mesh provided the best electrochemical performance. The Mo₈₀Ni₅Al₁₅ film deposited at 800 °C exhibited an overpotential of 176 mV at −10 mA cm⁻², a Tafel slope of 76 mV dec⁻¹, and the lowest charge-transfer resistance, demonstrating enhanced HER kinetics compared with pure Ni. Chronoamperometric measurements confirmed improved short-term stability, while corrosion measurements indicated acceptable resistance under alkaline conditions. X-ray photoelectron spectroscopy revealed electrochemically induced surface oxidation characterized by oxidation of Ni and Mo species and the formation of Ni³⁺-containing surface phases together with increased concentrations of oxidized Mo species after HER operation. Density functional theory calculations revealed that the optimized Ni-rich composition enhances the electronic hybridization between Ni and Mo, whereas the addition of Al alters the electronic density around the Fermi level without affecting the alloy's metallic properties, which supports efficient charge transfer. The combined electrochemical, spectroscopic, and theoretical results establish the structure–property relationship between alloy composition, electronic structure, surface chemistry, and HER performance. These findings demonstrate that simultaneous optimization of alloy composition and substrate selection represents an effective strategy for developing stable and efficient magnetron-sputtered PGM-free electrocatalysts for alkaline water electrolysis.