Hydrogen storage properties of Mg95-xNi5Ndx (x=0, 1, 3, 5) alloys

Abstract

In this work, Mg_95−xNi₅Nd_x(x = 0,1,3,5) alloys were successfully designed and prepared by induction melting combined with high-energy ball milling. The effects of the microstructure and phase evolution of the alloys on its kinetics and thermodynamics were analyzed by XRD, SEM, and PCT characterization methods. The results indicate that the alloys comprise the following phases: Mg, Mg₂Ni, Mg₄₁Nd₅, and Mg₁₂Nd phases. The hydrogen absorption reaction pathway of the alloy was Mg + Mg₂Ni + H₂→MgH₂ + Mg₂NiH₄、Mg₄₁Nd₅ + Mg₁₂Nd + H₂ → MgH₂ + Nd₂H₅, and the dehydrogenation reaction pathway was MgH₂ + Mg₂NiH₄→Mg + Mg₂Ni + H₂. The in-situ formed Nd₂H₅ phase remains stable and non-decomposable but is finely dispersed on the matrix surface. This phase exhibits catalytic activity, significantly enhancing the hydrogen storage performance of the alloy. As the Nd content increases, the dehydrogenation activation energy of the alloy decreases from 98.690 kJ/mol to 69.88 kJ/mol, which is the primary reason for the improvement in the alloy's hydrogen storage kinetics.