Speaker
Dr
Zuleyha Ozlem Kocabas Atakli
(Empa Materials Sciences and Technology, CH-8600 Dübendorf, Switzerland)
Description
Bogdanovic [1] presented the Ti-catalyzed hydrogen sorption in NaAlH4. The mechanism of the catalysis remains unclear despite the large number of proposed models. We presented a completely symmetric mechanism where the catalyst had a well-defined function. Firstly, we focused exclusively on understanding the main intermediate steps in the dehydrogenation and rehydrogenation of MAlH4 and M3AlH6 (where M= Li, Na, and K) based on thermodynamic considerations. In this manner, the Gibbs free energy values of each possible step were calculated based on experimental determined thermodynamic data (enthalpies and entropies) of individual hydrides, MAlH4, M3AlH6, and MH. Secondly, the values for the activation energies, based on the intermediates MH and AlH3 were obtained. Lastly, we presented an atomistic model, where the catalyst acted as a bridge to transfer the M+ and H- from AlH4- to AlH63- and finally to form MH based on thermodynamic considerations. The proposed mechanism is symmetric and the catalyst is active on the intermediates NaH and AlH3 for the hydrogen de- and absorption.
[1] B. Bogdanovic, M Schwickardi J. Alloys Compd., 253-254 (1997), pp. 1.
Author
Dr
Zuleyha Ozlem Kocabas Atakli
(Empa Materials Sciences and Technology, CH-8600 Dübendorf, Switzerland)
Co-authors
Dr
Andreas Zuttel
(Ecole polytechnique fédérale de Lausanne (EPFL), SB, ISIC, CH-1015 Lausanne, Switzerland)
Dr
Elsa Callini
(Empa Materials Sciences and Technology, CH-8600 Dübendorf, Switzerland)
Dr
Shunsuke Kato
(Empa Materials Sciences and Technology, CH-8600 Dübendorf, Switzerland)
