Thermodynamic performance of vanadium-modified Mg2Ni alloy for hydrogen storage

Abstract

This study investigates the effect of vanadium (V) addition on the hydrogen storage performance of Mg-Ni alloys prepared via high-energy ball milling (HEBM). The kinetic and thermodynamic properties of the composites were investigated by using analytical methods such as XRD, TEM, SEM, and PCT, and the modification patterns of Mg-Ni–based alloys with different contents of V particles were described. The results indicate that V does not alloy with Mg₂Ni but exists as interstitial particles, enhancing the microstructure and improving the hydrogen storage properties of the alloys. The alloy exhibits a flat pressure-composition curve, which indicates that the alloy reaches thermodynamic equilibrium during hydrogenation and the metallic phase coexists with the hydride phase. The apparent activation energy (E_des) for dehydrogenation decreased with increasing V content, from 32.04 kJ/mol for (Mg₂Ni)₉V₁ to 28.94 kJ/mol for (Mg₂Ni)₅V₅, suggesting improved kinetic properties. Thermodynamic parameters, such as enthalpy change (ΔH) and entropy change (ΔS), were also calculated, showing a reduction in ΔH with increasing V content, which enhances the hydrogen storage capacity. The findings demonstrate that the addition of V significantly improves the hydrogen storage performance of Mg-Ni alloys, making them promising as advanced hydrogen storage materials for practical applications.