TY - JOUR
T1 - The catalyzed hydrogen sorption mechanism in alkali alanates
AU - Kocabas Atakli, Züleyha Özlem
AU - Callini, Elsa
AU - Kato, Shunsuke
AU - Mauron, Philippe
AU - Orimo, Shin Ichi
AU - Züttel, Andreas
N1 - Publisher Copyright:
This journal is © the Owner Societies 2015.
PY - 2015/8/28
Y1 - 2015/8/28
N2 - The hydrogen sorption pathways of alkali alanates were analyzed and a mechanism for the catalytic hydrogen sorption was developed. Gibbs free energy values of selected intermediate steps were calculated based on experimentally determined thermodynamic data (enthalpies and entropies) of individual hydrides: MAlH4, M3AlH6, and MH. The values of the activation energies, based on the intermediates M+, H-, MH, and AlH3, were obtained. The mechanism of the catalytic activity of Ti is finally clarified: we present an atomistic model, where MAlH4 desorbs hydrogen through the intermediates M+, H-, MH, and AlH3 to the hexahydride M3AlH6 and finally the elemental hydride MH. The catalyst acts as a bridge to transfer M+ and H- from MAlH4- to the neighboring AlH4-, forming AlH63- and finally isolated MH, leaving AlH3 behind, which spontaneously desorbs hydrogen to give Al and 1.5H2. The proposed mechanism is symmetric in the direction of hydrogen desorption as well as readsorption processes.
AB - The hydrogen sorption pathways of alkali alanates were analyzed and a mechanism for the catalytic hydrogen sorption was developed. Gibbs free energy values of selected intermediate steps were calculated based on experimentally determined thermodynamic data (enthalpies and entropies) of individual hydrides: MAlH4, M3AlH6, and MH. The values of the activation energies, based on the intermediates M+, H-, MH, and AlH3, were obtained. The mechanism of the catalytic activity of Ti is finally clarified: we present an atomistic model, where MAlH4 desorbs hydrogen through the intermediates M+, H-, MH, and AlH3 to the hexahydride M3AlH6 and finally the elemental hydride MH. The catalyst acts as a bridge to transfer M+ and H- from MAlH4- to the neighboring AlH4-, forming AlH63- and finally isolated MH, leaving AlH3 behind, which spontaneously desorbs hydrogen to give Al and 1.5H2. The proposed mechanism is symmetric in the direction of hydrogen desorption as well as readsorption processes.
UR - http://www.scopus.com/inward/record.url?scp=84938651063&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84938651063&partnerID=8YFLogxK
U2 - 10.1039/c5cp01684c
DO - 10.1039/c5cp01684c
M3 - Article
AN - SCOPUS:84938651063
SN - 1463-9076
VL - 17
SP - 20932
EP - 20940
JO - Physical Chemistry Chemical Physics
JF - Physical Chemistry Chemical Physics
IS - 32
ER -