Towards understanding the role of the titanium in the hydrogenation and dehydrogenation of sodium alanate: A hybrid density functional study

INOR 652

Cristian V. Diaconu, cvdiaconu@lanl.gov, Theoretical Division, Group T-12, Los Alamos National Laboratory, MS B268, Los Alamos, NM 87545, J. D. Doll, Department of Chemistry, Brown University, 324 Brook Street, Providence, RI 02912, and David L. Freeman, Department of Chemistry, University of Rhode Island, Kingston, RI 02881.
We use the hybrid density functional theory to investigate the energetics of a number of titanium-, aluminum-, and hydrogen- containing molecules that we deem relevant for the titanium-catalyzed hydrogenation and dehydrogenation of sodium alanate. We first inventory the relevant simple molecules such as aluminum and titanium hydrides. From the broad trends observed for these simple molecules, we then study the relative stability of different "titanium alanates", molecules of the form TiAlnHm (n=1...4, m=4...16). The most stable molecule from our calculations is [Ti(AlH3)4]-1, implying that titanium prefers +3 oxidation state. However, we also find stable molecules in which titanium has lower oxidation numbers, such as Ti(AlH3)4. Here, Ti has a formally zero oxidation state and, possibly, forms Ti-Al bonds. We suggest a few possible pathways in which titanium could act as a catalyst in the hydrogenation and dehydrogenation of sodium alanate.
 

Computational Chemistry
7:00 PM-10:00 PM, Tuesday, 12 September 2006 Moscone Center -- Hall D, Poster

Division of Inorganic Chemistry

The 232nd ACS National Meeting, San Francisco, CA, September 10-14, 2006