Catalytic effect of Nb2O5 on dehydrogenation kinetics of NaAlH4

• NaAlH4 is an important hydrogen storage material with 5.6 wt% hydrogen content.
• Nb2O5 is a promising catalyst for the hydrogen desorption from sodium alanate
• Dehydrogenation of NaAlH4 converts it to a great extent to Na3AlH6.
• Nb2O5 doped NaAlH4 desorbed 5.0 wt% hydrogen less than theoretical capacity of 5.6%.
• .Catalyst reduces hydrogen desorption temperature from 285 °C to 250 °C.

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 (Nb2O5) and titanium cholride (TiCl3) catalysts are used to dehydrogenate NaAlH4. Structure and morphology of materials are characterized by XRD and SEM techniques. Sodium alanate was found to have tetragonal structure having a = 5.02 Å, b = 5.02 Å and c = 11.34 Å lattice parameters. Dehydrogenation of NaAlH4 at 250 °C converts it to a great extent to Na3AlH6 with lattice parameter a = b = c = 7.755 Å, 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 %.