| AVS 54th International Symposium | |
| Renewable Energy Science & Technology Topical Conference | Wednesday Sessions |
| Session EN+SS+TF-WeM |
| Session: | Catalysis for Hydrogen Storage and the Hydrogen Economy |
| Presenter: | S.C. Chaudhuri, Washington State University |
| Authors: | S.C. Chaudhuri, Washington State University J.-F. Veyan, Rutgers, The State University of New Jersey S.C. Schaäfer, Rutgers, The State University of New Jersey J.T. Muckerman, Brookhaven National Laboratory Y.J. Chabal, Rutgers, The State University of New Jersey |
| Correspondent: | Click to Email |
Complex metal hydrides, such as NaAlH4, are candidates for hydrogen storage because they can reversibly release and recapture hydrogen under near ambient conditions. Surface processes in the hydrogen storage reaction in NaAlH4, starting from a depleted phase consisting of NaH and metallic Al, and proceeding via cryolite Na3AlH6 to the hydrogen-rich NaAlH4, are considered as the basis for understanding reversible hydrogen storage in the chosen prototype system. Since metallic Al, particularly when doped with other metals, appear key to H2 dissociation, we have undertaken a comprehensive study of H interaction with Al(111) and Ti-doped Al(111) surfaces to better understand the atomic scale mechanisms underlying this reversible hydrogen storage behavior. We have combined in-situ infrared absorption spectroscopy with first principles calculations to investigate the reaction of atomic hydrogen reacts with Al surfaces. As previously observed,1 IR spectra show that alanes are formed upon H exposure. Alanes are highly mobile species at or near room temperature and desorb from Al(111) surfaces at higher temperatures mainly as AlH, AlH3 and Al2H6.2 Using FT-IR we show that the size of the alanes formed on Al(111) depend on the temperature of the sample. For low temperatures (Ã90K), small alanes such as AlH3 and Al2H6 are predominant. At higher temperatures (Ã250K), bigger alanes are formed. When the Al(111) surfaces are doped with 5% Ti, the Ti containing sites are reactive, dissociating molecular hydrogen, and thus act as a pump to generate hydride species on Al surfaces that subsequently convert into alanes. LEED is used to test the validity of first principles c alculations predicting that Ti atoms occupy hollow sites on the Al(111) surface. Using TPD, the nature of desorbed species from Al(111) and Ti-doped Al(111) surfaces have been analyzed as a function of the sample temperature after either atomic H or H2 exposures. This presentation summarizes hydrogen dissociation on Ti/Al(111), and alane formation and mobility on both Al(111) and Ti/Al(111) surfaces.
1 Eden P. Go, Konrad Thuermer, Janice E. Reutt-Robey, Surf. Sci. 437 (1999) 377
2Hara, M.; Domen, K.; Onishi, T.; Nozoye, H., J. Phys. Chem., 95, (1), (1991) 6-7