Abstract: Ti-doped NaAlH4 complex hydride can be prepared by hydrogenation of the ball-milled (NaH/Al+Ti) composite using NaH and pre-treated Al powder as raw materials, and Ti powder as a dopant. The influence of preparation parameters (ball-milling atmosphere, milling time, and hydrogenation pressure) on its hydrogen storage characteristic has been investigated. It is found that the hydrogen storage properties are affected greatly by the preparation methods. The hydrogen storage properties of the composite ball-milled under hydrogen atmosphere are better than that of the composite ball-milled under argon atmosphere. With extending the milling time from 6 h to 24 h under hydrogen atmosphere, the hydrogen absorption capacity and rate increase first and then decrease, and the maximum values are obtained at 12 h, while the hydrogen desorption capacity and speed increase gradually. The particles of the composite will agglomerate when prolonging the milling-time over 12 h, which deteriorates the hydrogen absorption properties. As the hydrogenation pressure increases from 7.5 MPa to 13.5 MPa, the hydrogen absorption storage capacity (mass fraction) increases from 2.83% to 4.21%. The appearance of intermediate Na3AlH6 hydride phase in the ball-milled composite indicates that the Ti-doped (NaH/Al) composites ball-milled under hydrogen atmosphere can catalyze the hydrogenation reaction of NaH and Al.

Key words: Complex hydrides, Hydrogen storage characteristic, Catalysis, NaAlH4, Ti-doped