Abstract The reversible hydrogen storage properties of Ti-catalyzed NaAlH 4 (and associated Na 3 AlH 6 ) were studied as a function of Ti-content using a dry preparation technique consisting of the ball-milling of NaAlH 4 +TiCl 3 mixtures (0–9 mol.% TiCl 3 ). This process is believed to result in the in situ solid-state introduction of metallic Ti via the reduction of the TiCl 3 by the Na-component of NaAlH 4 (to form NaCl). Properties studied were hydriding and dehydriding rates and reversible gravimetric H-capacity as a function of starting TiCl 3 content. Detailed isothermal kinetic studies were done over a wide temperature range (20–225 °C) and treated by Arrhenius analysis. All kinetics were found to follow the Arrhenius equation and the changes of thermal activation energies and rate constants with TiCl 3 -content were observed that may give valuable insights into the as-yet unknown mechanistic factors that control H 2 desorption and absorption kinetics. Ti increases both dehydriding and hydriding kinetics (and associated practical engineering rates), but at the substantial expense of H-capacity. The finite room temperature decomposition of the catalyzed NaAlH 4 phase was reconfirmed and rates better quantified.
[1]
Craig M. Jensen,et al.
Hydrogen cycling behavior of zirconium and titanium–zirconium-doped sodium aluminum hydride
,
1999
.
[2]
G. Sandrock,et al.
HYDRIDE DEVELOPMENT FOR HYDROGEN STORAGE
,
1996
.
[3]
B. Bogdanovic,et al.
Ti-doped alkali metal aluminium hydrides as potential novel reversible hydrogen storage materials
,
1997
.
[4]
R. Brand,et al.
Metal-doped sodium aluminium hydrides as potential new hydrogen storage materials
,
2000
.
[5]
Craig M. Jensen,et al.
Development of catalytically enhanced sodium aluminum hydride as a hydrogen-storage material
,
2001
.
[6]
K. Gross,et al.
In-situ X-ray diffraction study of the decomposition of NaAlH4
,
2000
.
[7]
H. Fjellvåg,et al.
The Structures of Hydride Phases in the Ti3Al/H System
,
1999
.
[8]
Craig M. Jensen,et al.
Advanced titanium doping of sodium aluminum hydride:: segue to a practical hydrogen storage material?
,
1999
.