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M: Metallphysik

M 4: Wasserstoff in Metallen

M 4.3: Vortrag

Freitag, 4. März 2005, 11:00–11:15, TU H2038

Characterization of the dehydrogenation of alanates with different catalyst monitored by proton NMR — •Laura Esther Valiente-Banuet, Eva Stanik, and Günter Majer — Max-Planck-Institut für Metallforschung, Heisenbergstr. 3, 70569 Stuttgart

NaAlH₄ is a promising material for the development of reversible hydrogen storage systems. The kind of pre-treatment of the material and the catalyst play a crucial role in the increase of the de- and re-hydriding rates. This also influences the reduction in the temperature of dehydrogenation. However, the microscopic mechanism and the change of the hydrogen mobility due to the catalyst are not yet completely understood. In this work we report on NMR studies of the hydrogen desorption from NaAlH₄ doped with the catalysts TiCl₃ and Ti₁₃-clusters, respectively. The time dependence of the NMR spectra, measured at a given temperature, shows clearly the transition from NaAlH₄ to Na₃AlH₆. The hydrogen dynamics in the different compounds is investigated by measurements of the spin-lattice relaxation. In the case of NaAlH₄ a double-exponential recovery of the nuclear magnetization is observed, which indicates two fractions of hydrogen with different mobilities.