Method for preparing Ti-doped NaAlH4 using Ti powder: observation of an unusual reversible dehydrogenation behavior

Abstract Titanium powder can be directly used as dopant in the preparation of catalytically enhanced Ti-doped NaAlH 4 upon mechanical milling under an atmosphere of hydrogen. The hydrogen storage performance of NaAlH 4 that was doped through this method was found to be highly dependent on the milling time. A sample mechanically milled under hydrogen for 10 h was initially observed to discharge >3.3 wt.% of hydrogen within 1 h at 150 °C. Rehydrogenation was accomplished at 120 °C under about 12 MPa H 2 within 10 h. The hydrogen capacity of this material was found to gradually decrease to 2.8 wt.% after eight cycles. The dehydriding kinetics and cycling properties of NaAlH 4 that is doped through this novel method is clearly distinct from the material that is obtained through the utilization of Ti(III) or Ti(IV) dopant precursors and milling under argon. This suggests that the nature of active Ti-species may differ in these two varieties of doped NaAlH 4 .

[1]  B. Bogdanovic,et al.  Ti-doped NaAlH4 as a hydrogen-storage material – preparation by Ti-catalyzed hydrogenation of aluminum powder in conjunction with sodium hydride , 2001 .

[2]  A. Załuska,et al.  Sodium alanates for reversible hydrogen storage , 2000 .

[3]  G. Meisner,et al.  Phase changes and hydrogen release during decomposition of sodium alanates , 2003 .

[4]  G. Sandrock,et al.  Dynamic in-situ X-ray Diffraction of Catalyzed Alanates , 2000 .

[5]  Dalin Sun,et al.  X-ray diffraction studies of titanium and zirconium doped NaAlH4: elucidation of doping induced structural changes and their relationship to enhanced hydrogen storage properties , 2002 .

[6]  Ferdi Schüth,et al.  Improved Hydrogen Storage Properties of Ti‐Doped Sodium Alanate Using Titanium Nanoparticles as Doping Agents , 2003 .

[7]  Craig M. Jensen,et al.  Advanced titanium doping of sodium aluminum hydride:: segue to a practical hydrogen storage material? , 1999 .

[8]  K. Gross,et al.  In-situ X-ray diffraction study of the decomposition of NaAlH4 , 2000 .

[9]  K. Gross,et al.  Catalyzed alanates for hydrogen storage , 2000 .

[10]  G. Meisner,et al.  Enhancing low pressure hydrogen storage in sodium alanates , 2002 .

[11]  S. Srinivasan,et al.  Kinetic study and determination of the enthalpies of activation of the dehydrogenation of titanium- and zirconium-doped NaAlH4 and Na3AlH6 , 2003 .

[12]  G. Sandrock,et al.  Catalyzed Complex Metal Hydrides , 2002 .

[13]  Nancy Y. C. Yang,et al.  Microstructural characterization of catalyzed NaAlH4 , 2002 .

[14]  G. Sandrock,et al.  Effect of Ti-catalyst content on the reversible hydrogen storage properties of the sodium alanates , 2002 .

[15]  G. Sandrock,et al.  Engineering considerations in the use of catalyzed sodium alanates for hydrogen storage , 2002 .

[16]  Ferdi Schüth,et al.  Investigation of hydrogen discharging and recharging processes of Ti-doped NaAlH4 by X-ray diffraction analysis (XRD) and solid-state NMR spectroscopy , 2003 .

[17]  B. Bogdanovic,et al.  Ti-doped alkali metal aluminium hydrides as potential novel reversible hydrogen storage materials , 1997 .

[18]  Craig M. Jensen,et al.  Hydrogen cycling behavior of zirconium and titanium–zirconium-doped sodium aluminum hydride , 1999 .

[19]  R. Brand,et al.  Metal-doped sodium aluminium hydrides as potential new hydrogen storage materials , 2000 .

[20]  Craig M. Jensen,et al.  Development of catalytically enhanced sodium aluminum hydride as a hydrogen-storage material , 2001 .

[21]  M. Fichtner,et al.  Synthesis and structures of magnesium alanate and two solvent adducts , 2002 .

[22]  M. Fichtner,et al.  Small Ti clusters for catalysis of hydrogen exchange in NaAlH4 , 2003 .