Abstract: The NaAlH4 complex hydride was prepared by hydrogenation of the ball-milled (NaH/Al+Ti) and (NaH/Al+Ti-Zr) composites. The influences of Ti and Ti-Zr catalysts, different hydriding temperatures and pressures on its reversible hydrogen storage behaviors were investigated. It was found that the catalysis of Ti-Zr powders as co-catalysts on the dehydriding/hydriding characteristics of NaH/Al was better than that of Ti alone as catalyst. As the hydriding temperature increased from 85 ℃ to 140 ℃, the hydrogen absorption capacity increased first and then decreased, and reached the highest value at 120 ℃. The composite co-doped with Ti-Zr catalysts had the best reversible hydrogen storage properties, its hydrogen storage capacities were 4.61%(w) at 120 ℃ and 3.52%(w) at 85 ℃, which were 0.40% and 0.70%(w) higher than that doped with Ti alone as catalyst in the same hydriding condition, respectively. The hydrogen storage performance of (NaH/Al+Ti-Zr) composite was enhanced with the increase of hydriding pressure. XRD and DSC analyses showed that the dehydriding process of NaAlH4 system took place in two steps. The composite co-doped with Ti-Zr catalysts could improve the dehydriding/hydriding kinetics of NaAlH4 systemand reduced its dehydriding temperature. That was the main reason of the hydrogen storage characteristic of the composites co-doped with Ti-Zr catalysts better than that doped with Ti catalyst alone.

Key words: Complex hydride, NaAlH4, Ti-Zr-doped, Ball-milling, Hydrogen storage characteristics