Phase transformation, thermodynamics and kinetics property of Mg90Ce5RE5 (RE = La, Ce, Nd) hydrogen storage alloys

Abstract The Mg90Ce5RE5 (RE = La, Ce, Nd) alloys were prepared by a vacuum induction furnace and their microstructure, phase transformation, thermodynamics and kinetics property were systematically studied by XRD, SEM, TEM, and PCT characterization methods. The result shows that the activated alloys are composed of Mg/MgH2 and corresponding REH2+x with nanoscale. The REH2+x grain with Ce and La or Nd functional group have lower nucleation potential barriers than CeH2+x grains as the nucleation location, thus improve the hydrogen absorption kinetics of these alloys among which the Mg90Ce5Nd5 alloy can absorb 90% of the hydrogen within 2 min at 320 oC. In addition, the Mg90Ce10 alloy has the lowest activation energy with 103.2 kJ mol-1 and the fastest desorption kinetics, which can release 5 wt% of the hydrogen within 20 min at 320 oC. This is a correlation with grain size and the in-suit formed CeH2.73/CeO2 interface. Moreover, the co-doping Ce and La or Nd can effectively disorganize the thermodynamic stability of Mg-based hydrogen storage alloys to a certain degree, but the dehydrogenation kinetics of that still is restricted by the recombination energy of hydrogen ions on the surface.