Dehydrogenation kinetics of Ti-doped NaAlH4 - Influence of Ti precursors and preparation methods

We investigated at 423K in vacuo the hydrogen desorption kinetics of Ti-doped sodium aluminum hydride (NaAlH4) prepared with using different Ti precursors and procedures. Initial distinction in kinetics among specimens vanishes through several cycles of dehydrogenation at 473K in uacuo and rehydrogenation at 423K under 10 MPa of H-2. Considering that the temperature of dehydrogenation cycle is above the melting point of NaAlH4, we can assume that the difference in physical nature of the materials, such as particle size, phase distribution and so on, disappears through cycling. The present study tells that the chemical nature of the Ti related species which enhances the reaction kinetics of alanate becomes identical whatever Ti presursor is used and, however, the material is prepared. (C) 2007 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.