The Structure of Li-N-H-Al-Cl Phases for the Reversible Hydrogen Storage Properties from X-ray and Neutron Diffraction

L. FERNÁNDEZ ALBANESI; S. GARRONI; P. ARNEODO LAROCHETTE; P. NOLIS; G. MULAS; S. ENZO; M. D. BARÓ; F. C. GENNARI; E. NAPOLITANO

París

Simposio; 22nd International Symposium on Metastable, Amorphous and Nanostructured Materials; 2015

ISMANAM

In recent work we investigated the hydrogen storage properties of the AlCl3-doped LiNH2-1.6LiH composites and assessed advantageous hydrogen storage performance. The dehydrogenation rate from these composites was three-fold and six-fold faster than for un-doped LiNH2-1.6LiH, depending of the Al content in the sample. Also, the re-hydrogenation kinetics was found faster for doped material, leading to good reversibility in the cycles. Moreover, the addition of relatively higher amount of AlCl3 leads to the formation of new amide-chloride aluminum phases through a solid state reaction by ball milling. The product of such process appears as a sequence of peaks belonging to a face centered cubic (FCC) scheme, with small lattice parameter value around 5.15-5.22 Å. Subsequent thermal treatments at 150 and 300 °C leads to the formation of new symmetries having increased lattice parameters and belonging to cubic and trigonal systems, respectively. Our interpretation for powder X-ray and neutron diffraction patterns is supplemented by FT-IR and SS-MAS-NMR data and is expected to solve the new observed (metastable) phases, i.e., by assigning the space group and precisely locating the atomic species in the sites of the unit cell. The structural modifications introduced in the Li-N-H system after addition of AlCl3 and subsequent to the thermal treatments allows us to clarify the mechanism that enhances the hydrogen sorption properties.