An ab initio study of possible pathways in the thermal decomposition of NaAlH4

Ojwang, Jgo Julius; Santen, Rutger A. van; Kramer, GJ Gert Jan; Ke, Xuezhi

doi:10.1016/j.jssc.2008.08.010

Cited by 10 publications

(10 citation statements)

References 29 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The reaction most likely proceeds via intermediates such as [Na 2 AlH 5 ] 14 or [Na 5 Al 3 H 14 ], 42 although neither of these has been detected experimentally. However, as far as our present discussion is concerned, the actual elementary steps are not relevant.…”

Section: Dehydrogenation Of Naalh 4 In the Presence Of A Catalystmentioning

confidence: 99%

Formation of Al2H7− anions — indirect evidence of volatile AlH3 on sodium alanate using solid-state NMR spectroscopy

Felderhoff

Zibrowius

2011

Phys. Chem. Chem. Phys.

View full text Add to dashboard Cite

After more than a decade of intense research on NaAlH(4) doped with transition metals as hydrogen storage material, the actual mechanism of the decomposition and rehydrogenation reaction is still unclear. Early on, monomeric AlH(3) was named as a possible transport shuttle for aluminium, but never observed experimentally. Here we report for the first time the trapping of volatile AlH(3) produced during the decomposition of undoped NaAlH(4) by an adduct of sodium alanate and crown ether. The resulting Al(2)H(7)(-) anion was identified by solid-state (27)Al NMR spectroscopy. Based on this indirect evidence of volatile alane, we present a simple description of the processes occurring during the reversible dehydrogenation of NaAlH(4).

show abstract

Section: Dehydrogenation Of Naalh 4 In the Presence Of A Catalystmentioning

confidence: 99%

Formation of Al2H7− anions — indirect evidence of volatile AlH3 on sodium alanate using solid-state NMR spectroscopy

Felderhoff

Zibrowius

2011

Phys. Chem. Chem. Phys.

View full text Add to dashboard Cite

show abstract

“…Ojwang et al 72 investigated the structure of Na 5 Al 3 H 14 by using DFT study. Na 5 Al 3 H 14 is crystallized in the space group P4/mnc with two formula units per unit cell and it is one of the possible intermediates of the thermal decomposition of NaAlH 4 .…”

Section: Na 5 Al 3 H 14mentioning

confidence: 99%

Crystal structures of aluminum-based hydrides

Vajeeston¹,

Fjellvåg²

2015

Emerging Materials Research

View full text Add to dashboard Cite

The interest of hydrogen as the future energy is that it is a clean energy carrier, most abundant element in the universe, the lightest fuel, richest in energy per unit mass and unlike electricity it can be easily stored. Hydrogen gas is the most promising fuel for various applications. Hydrogen is already being used as the fuel of choice for space programs around the world. Metal hydrides are a fascinating class of compounds, because the small mass and size of hydrogen and its medium electronegativity cause a large flexibility in terms of metal-ligand interactions. These manifest itself in a vast variety of possible compositions, chemical bonding, crystal structures and physical properties. In this review, we presented the structural details of all up-to-date known Al-based hydrides.

show abstract

“…The second step, in which Na 3 AlH 6 reacts to NaH, Al, and H 2 , proceeds at close to 110 °C. There has been speculation on the role of intermediate Na n Al m H l phases, and structural similarities between NaAlH 4 phases and Na 3 AlH 6 have been invoked to explain the good de(re)hydrogenation properties of the material. , A key point is that the release and reuptake of H 2 can be made reversible by adding a catalyst like Ti, as demonstrated in 1997 by Bogdanovic and Schwickardi . In much of the subsequent work aimed at improving the kinetics of the release and reuptake of H 2 , Ti was used (in the form of TiCl 3 or of colloid nanoparticles , ).…”

Section: Introductionmentioning

confidence: 99%

Effect of Transition Metal Dopants on Initial Mass Transport in the Dehydrogenation of NaAlH₄: Density Functional Theory Study

et al. 2012

View full text Add to dashboard Cite

Sodium alanate (NaAlH4) is a prototype system for storage of hydrogen in chemical form. However, a key experimental finding, that early transition metals (TMs) like Ti, Zr, and Sc are good catalysts for hydrogen release (and reuptake) whereas traditional hydrogenation catalysts like Pd and Pt are poor catalysts for NaAlH4, has so far received little attention. We performed density functional theory (DFT) calculations at the PW91 generalized gradient approximation level on Ti, Zr, Sc, Pd, and Pt interacting with the (001) surface of nanocrystalline NaAlH4, employing a cluster model of the complex metal hydride to study the initial mass transport in the dehydrogenation process. A key difference between Ti, Zr, and Sc on one hand and Pd and Pt on the other is that exchange of the early TM atoms with a surface Na ion, whereby Na is pushed on to the surface, is energetically preferred over surface absorption in an interstitial site, as found for Pd and Pt. These theoretical findings are consistent with a crucial feature of the TM catalyst being that it can be transported with the reaction boundary as it moves into the bulk, enabling the starting material to react away while the catalyst eats its way into the bulk and affecting a phase separation between a Na-rich and an Al-rich phase. Additional periodic DFT/PW91 calculations in which NaAlH4 is modeled as a slab to model dehydrogenation of larger NaAlH4 particles and which only consider adsorption and absorption of Ti suggest that Ti prefers to absorb interstitially but with only a small energy preference over a geometry in which Ti has exchanged with Na. Additional nudged elastic band calculations based on periodic DFT show only a small barrier (0.02 eV) for exchange of Ti with a surface Na atom. The mechanism inferred from the cluster calculations is therefore consistent with the slab calculations and may well be important.

show abstract

An ab initio study of possible pathways in the thermal decomposition of NaAlH4

Cited by 10 publications

References 29 publications

Formation of Al2H7− anions — indirect evidence of volatile AlH3 on sodium alanate using solid-state NMR spectroscopy

Formation of Al2H7− anions — indirect evidence of volatile AlH3 on sodium alanate using solid-state NMR spectroscopy

Crystal structures of aluminum-based hydrides

Effect of Transition Metal Dopants on Initial Mass Transport in the Dehydrogenation of NaAlH₄: Density Functional Theory Study

Contact Info

Product

Resources

About

An ab initio study of possible pathways in the thermal decomposition of NaAlH4

Cited by 10 publications

References 29 publications

Formation of Al2H7− anions — indirect evidence of volatile AlH3 on sodium alanate using solid-state NMR spectroscopy

Formation of Al2H7− anions — indirect evidence of volatile AlH3 on sodium alanate using solid-state NMR spectroscopy

Crystal structures of aluminum-based hydrides

Effect of Transition Metal Dopants on Initial Mass Transport in the Dehydrogenation of NaAlH4: Density Functional Theory Study

Contact Info

Product

Resources

About

Effect of Transition Metal Dopants on Initial Mass Transport in the Dehydrogenation of NaAlH₄: Density Functional Theory Study