Catalytic effect of Nb2O5 on dehydrogenation kinetics of NaAlH4

摘要

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 angstrom, b = 5.02 angstrom and c = 11.34 angstrom lattice parameters. Dehydrogenation of NaAlH4 at 250 degrees C converts it to a great extent to Na3AlH6 with lattice parameter a = b = c = 7.755 angstrom, 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 %. (C) 2015 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.