Enhanced hydrogen storage kinetics of an Mg–Pr–Al composite by in situ formed Pr3Al11 nanoparticles

Abstract

Slow hydrogen sorption kinetics is one of the challenges facing practical applications of MgH₂. To improve the hydrogen sorption kinetics, an Mg–Pr–Al composite is prepared by ball milling of a 14MgH₂ + Pr + Al powder mixture. During hydrogenation and dehydrogenation processes of the Mg–Pr–Al composite, two reversible side reactions, i.e. 2PrH₂ + H₂ = 2PrH₃ and Mg₁₇Al₁₂ + 17H₂ = 17MgH₂ + 12Al, occur accompanying hydrogen adsorption and desorption of the Mg–H₂ system. The in situ formed Pr₃Al₁₁ phase in the activated Mg–Pr–Al composite is stable during further hydrogen adsorption and desorption processes, which plays a role in inhibiting growth of Mg crystallites. Hence, the improvement of hydrogen sorption kinetics for the Mg–Pr–Al composite is ascribed to the inhibiting role of Pr₃Al₁₁ in crystallite growth as well as the catalytic effect of PrH₃/PrH₂ on hydrogen sorption. These findings provide an important guidance for developing new Mg-based materials with superior hydrogen storage properties.