The hydrogen storage properties and microstructure of Ti-doped sodium aluminum hydride prepared by ball-milling

The hydrogen storage properties and microstructures of Ti-doped NaAlH 4 complex hydrides prepared by hydrogenation of ball-milled NaH/Al mixture with x mol% Ti powder ( x = 0 , 4 , 6 , 10 ) were investigated. It is found that hydrogen as ball-milling atmosphere is better than argon. The reversible hydrogen storage properties improve with increasing Ti content. As the milling time ( t ) extends from 1 to 24 h, the hydrogen desorption capacity increases first and then decreases, and reaches a maximum capacity of 4.25 wt% at t = 16 . The catalytic mechanism for hydrogen storage behavior of Ti-doped NaAlH 4 is attributed to the presence of active small TiH 1.924 and TiAl particles, which are scattered on the surface of much larger NaAlH 4 (NaH/Al) globelets, acting as the catalytic active sites for the complex compound and playing an important catalytic role in the hydriding-dehydriding process.