Thermochemistry of Alane Complexes for Hydrogen Storage: A Theoretical and Experimental Investigation

Journal Article · Wed Mar 30 04:00:00 EDT 2011 · The Journal of Physical Chemistry

DOI:https://doi.org/10.1021/jp112258s· OSTI ID:1040447

Wong, B M; Graetz, J; Lacina, D; Nielsen, I M.B.; Allendorf, M D

Knowledge of the relative stabilities of alane (AlH{sub 3}) complexes with electron donors is essential for identifying hydrogen storage materials for vehicular applications that can be regenerated by off-board methods; however, almost no thermodynamic data are available to make this assessment. To fill this gap, we employed the G4(MP2) method to determine heats of formation, entropies, and Gibbs free energies of formation for 38 alane complexes with NH{sub 3-n}R{sub n} (R = Me, Et; n = 0-3), pyridine, pyrazine, triethylenediamine (TEDA), quinuclidine, OH{sub 2-n}R{sub n} (R = Me, Et; n = 0-2), dioxane, and tetrahydrofuran (THF). Monomer, bis, and selected dimer complex geometries were considered. Using these data, we computed the thermodynamics of the key formation and dehydrogenation reactions that would occur during hydrogen delivery and alane regeneration, from which trends in complex stability were identified. These predictions were tested by synthesizing six amine-alane complexes involving trimethylamine, triethylamine, dimethylethylamine, TEDA, quinuclidine, and hexamine and obtaining upper limits of {Delta}G{sup o} for their formation from metallic aluminum. Combining these computational and experimental results, we establish a criterion for complex stability relevant to hydrogen storage that can be used to assess potential ligands prior to attempting synthesis of the alane complex. On the basis of this, we conclude that only a subset of the tertiary amine complexes considered and none of the ether complexes can be successfully formed by direct reaction with aluminum and regenerated in an alane-based hydrogen storage system.

• Research Organization: BROOKHAVEN NATIONAL LABORATORY (BNL)
• Sponsoring Organization: USDOE SC OFFICE OF SCIENCE (SC)
• DOE Contract Number: AC02-98CH10886
• OSTI ID: 1040447
• Report Number(s): BNL--95291-2011-JA; KC0202020
• Journal Information: The Journal of Physical Chemistry, Journal Name: The Journal of Physical Chemistry Journal Issue: 15 Vol. 115
• Country of Publication: United States
• Language: English

Related Subjects

08 HYDROGEN
25 ENERGY STORAGE
ALUMINIUM
AMINES
BINDING ENERGY
DEHYDROGENATION
DIMERS
DIOXANE
DIRECT REACTIONS
ELECTRONS
ETHERS
HYDROGEN
HYDROGEN STORAGE
PYRIDINE
REGENERATION
STABILITY
SYNTHESIS
TETRAHYDROFURAN
THERMODYNAMICS
VALENCE