Vanadium-enhanced Mg-Ni alloys: Advancing zero pollution and zero emission hydrogen storage for a circular economy

This study investigates the effect of varying vanadium (V) content on the hydrogen absorption/desorption kinetics of (Mg₂Ni)_10-xV_x (x = 1, 3, 5) alloys prepared via high-energy ball milling. The results demonstrate that the addition of V enhances the hydrogenation reaction rate, activates the alloy, and accelerates hydrogen diffusion, with the (Mg₂Ni)₉V₁ alloy exhibiting the best hydrogen absorption performance at an optimal V content of 1. During hydrogen absorption, the alloys quickly reach hydrogen saturation in the rapid absorption stage, but the hydrogen absorption capacity decreases as V content increases. Desorption experiments reveal that the presence of V increases the temperature sensitivity of the hydrogen desorption process, with higher temperatures accelerating desorption. However, excessive V content slows down desorption kinetics. ICP and EDS analyses show that V is unevenly distributed on the alloy surface, and the surface effect of EDS may lead to inaccuracies in element distribution. Overall, the study concludes that a moderate amount of V substitution for Mg₂Ni improves the hydrogen absorption capacity, but excessive V content negatively impacts the hydrogen storage performance of the alloy.