| AVS 55th International Symposium & Exhibition | |
| Energy Science and Technology Focus Topic | Monday Sessions |
| Session EN+SE+NS+SS-MoA |
| Session: | Hydrogen Storage |
| Presenter: | I.S. Chopra, University of Texas at Dallas |
| Authors: | I.S. Chopra, University of Texas at Dallas J.-F. Veyan, University of Texas at Dallas Y.J. Chabal, University of Texas at Dallas S. Chaudhuri, Washington State University |
| Correspondent: | Click to Email |
Complex metal hydrides, such as NaAlH4, are candidates for hydrogen storage as they can reversibly release and recapture hydrogen. Alane Clusters (AlxHy) are believed to be the mass transport intermediate in the hydrogen storage reactions involved in hydrogen uptake and release. Understanding the surface chemistry behind the formation and evolution of alane clusters is therefore important to lower the temperatures needed for these processes. Since doping metallic Al is critical for H2 dissociation, we have undertaken a comprehensive study of H interaction with Al(100) and Ti-doped Al(100) surfaces to better understand the atomic scale mechanisms underlying this reversible hydrogen storage behavior. The results have been compared with similar study performed earlier on the Al(111) and Ti doped Al(111) surface. In-situ infrared absorption spectroscopy had previously shown1 that the nature of alanes (size, bonding configuration) formed on Al(111) depends on both H exposure and sample temperature. At low temperatures (~90K), small alanes such as AlH3 and Al2H6 are predominant. At higher temperatures (~ 250K), larger alanes are formed. The study of alane formation on the Al(100) surface as a function of H exposures and substrate temperatures make it possible to explore the dependence of the alane formation on the crystal orientation. The effect of Ti doping is also explored as a function of both Ti concentration and H2 pressures. Our first-principles calculations indicate that Ti atoms should occupy hollow sites of the (100) unit cell. We are therefore using LEED to test whether this site is indeed the most favorable and IR spectroscopy to explore whether Ti in that site does dissociate H2. On Al(111), no dissociation was observed for H2 pressure up to 10-6 Torr. We are therefore exploring dissociation up to 10-4 Torr on Al(100). Finally, we are using TPD to probe the nature of desorbed species from both Al(100) and Ti –doped Al(100) surfaces.
1 Santanu Chaudhuri, Sylvie Rangan, Jean-Francois Veyan, James T. Muckerman,Yves J. Chabal, J.Am. Chem. Soc. (submitted).