Catalytic effect of Nb2O5 on dehydrogenation kinetics of NaAlH4

Abstract Sodium alanate is an important hydrogen storage material with high hydrogen content of 7.5 wt%, but it does not release hydrogen easily. In the present work niobium oxide (Nb 2 O 5 ) and titanium cholride (TiCl 3) catalysts are used to dehydrogenate NaAlH 4. Structure and morphology of materials are characterized by XRD and SEM techniques. Sodium alanate was found to have tetragonal structure having a = 5.02 A, b = 5.02 A and c = 11.34 A lattice parameters. Dehydrogenation of NaAlH 4 at 250 °C converts it to a great extent to Na 3 AlH 6 with lattice parameter a = b = c = 7.755 A, living behind a very small amount of sodium alanate reflecting in XRD peak. Scanning electron microscopic studies shows reduction in particle size after dehydrogenation. The dehydrogenation kinetics of the samples was studied using dynamic Seivert type apparatus. The amount of desorbed hydrogen was found to be 4.8 and 5.0wt %.