Hydrogenation properties of MgNi_0.86Ml_0.03 (Ml=Cr, Fe, Co, Mn) alloys

Hydrogenation properties of amorphous MgNi_0.86M1^0.03 (M1=Cr, Fe, Co, Mn) alloys prepared by the mechanical alloying method were investigated. The Cr-substituted alloy desorbed 0.4 wt.% of hydrogen even at 423 K in the pressure range between 0.01 MPa and 1 MPa, and the enthalpy of hydride formation was calculated as -50 kJ mol^-1 H^-1₂. This value is the largest among Mg-based alloys. Therefore, the hydride of this alloy is the least stable among other Mg-based alloys. However, Mn or Co-substituted alloys did not desorb hydrogen at 423 K. The influence of the substitution element on the relationship between the site energy of hydrogen in amorphous alloys and the hydrogenation properties is explained. For practical use, the Cr-substituted alloy has good enough thermodynamic properties for hydrogen storage on hydrogen vehicles though the amount of desorbed hydrogen is insufficient.