Effect of RE Content on Microstructure and Hydrogen Storage Properties of Mg-RE-based Alloys

In order to investigate the influence of RE(La and Ce) and Ni content on the microstructure and hydrogen storage performance of magnesium-based alloys, Mg₉₀Ni<italic>_x</italic>RE_10-<italic>_x</italic>(<italic>x</italic> = 4,5,6) alloys are prepared using induction melting. The alloys are characterized and tested by XRD, SEM, EDS, and PCT. The results reveal that the alloy consists of phases of Mg, Mg₂Ni, CeMg₁₂, Ce₂Mg₁₇, LaMg₁₂, and La₂Mg₁₇. After hydrogen absorption, MgH₂, Mg₂NiH₄, CeH_2.29, and LaH_3.05 phases are formed, while the phases after hydrogen desorption include Mg, Mg₂Ni, CeH₂, and LaH₂. The results of hydrogen absorption and desorption kinetic test show that the optimal ratio of RE to Ni elements in the alloy is 1∶1, while the activation performance and hydrogen storage capacity are best. The maximum hydrogen absorption and desorption capacities are 5.21%and 5.19% (Mass fraction), respectively. The in situ formed REH<italic>_x</italic>and Mg₂Ni/Mg₂NiH₄ phase have synergistic catalyst effect on hydrogen transport in the alloy. The Mg₉₀Ni₅RE₅ alloy exhibits the lowest activation energy during hydrogen desorption reaction of 87.14 kJ/mol. Entropy change (Δ<italic>H</italic>) of the alloys, which are calculated by using the PCT data and the Van’t Hoff equation, have no significant relationship with the RE content.