An investigation on hydrogen storage thermodynamics and kinetics of Pr-Mg-Ni-based PrMg12-type alloys synthesized by mechanical milling

Mechanical ball milling technology was utilized to synthesize the nanocrystalline and amorphous PrMg11Ni + x wt% Ni (x = 100, 200) alloys. The effect of Ni content and milling time on thermodynamics and kinetics of the alloys were systematically investigated. The hydrogen absorption and desorption properties were analyzed by Sievert's apparatus and differential scanning calorimetry (DSC). Results show that increasing Ni content brings on a slight reduction in thermodynamic parameters (ΔH and ΔS) of the alloys, and it dramatically enhances the hydrogen absorption and desorption kinetics of the alloys. Varying milling time greatly affects the hydrogen storage properties of the alloys. The hydrogen absorption capacity of the alloys first increases and then deceases with the increase of milling time, and the maximum capacity of the alloy is approximately 5.8 wt% and 6.0 wt% for the x = 100 and x = 200 alloys. Moreover, the hydrogen desorption activation energy obviously decreases with increasing the Ni content and ball milling time.