Phase evolution, thermodynamics and kinetics property of transition metal (TM = Zr, Ti, V) catalyzed Mg–Ce–Y–Ni hydrogen storage alloys.

To improve hydrogen storage property of Mg-based alloy, the Mg–Ce–Y–Ni + 10 wt % M (M = Zr, Ti, V) composites were prepared by the combination of alloying and ball-milling, and their microstructure, phase evolution, as well as hydrogen storage thermodynamic and kinetic properties, were investigated by XRD, PCT, and DSC methods. The result shows that the hydrogenated samples are composed of MgH 2 , Mg 2 NiH 4 and corresponding ZrH 2 , TiH 2 and VH 1.9 phases. In comparison, the |Δ H| value of M = Ti sample is larger than that of M = Zr and M = V samples, and the M = Ti sample has the highest the peak temperatures and lowest plateau pressure, which indicates that Zr and V elements are more efficient to reduce the thermodynamic stability of RE-Mg-Ni hydrogen storage alloys. Besides, the DSC curve of the M = V sample has another endothermic peak which corresponds to the decomposition reaction between VH 1.9 and VH 0.8 , which has a contribution to desorption kinetic property for the M = V sample. The apparent activation energies (E de) show an increasing trend in the following order: M = Zr (87.7 kJ/mol) < M = V (89.1 kJ/mol) < M = Ti (99.3 kJ/mol). Because the reversible cycle between VH1.9 and VH0.8 provides the driving force to activate the hydrogen desorption of MgH 2, M V sample become an exception of the electronegative rule, and shows better dynamics property than M Ti sample. Image 1 • Mg–Ce–Y–Ni-TM composites are prepared by the combination of alloying and ball-milling. • The Zr and V elements are efficient to disorganize the thermodynamic Mg-based alloy. • The positive role of reversible reaction between the VH 1.9 and VH 0.8 is confirmed. • Activation energy is determined by the both of element property and reaction path. [ABSTRACT FROM AUTHOR]