Role of AlCl3 additive on the reversible hydrogen storage of the Li-N-H system

L. FERNÁNDEZ ALBANESI; S. GARRONI; M. D. BARÓ; P. NOLIS; P. ARNEODO LAROCHETTE; F. C. GENNARI

Rio de Janeiro

Conferencia; International Conference on hydrogen Storage Embrittlement and Applications HySEA 2014; 2014

COPPE/UFRJ, Brazil

Light metal amides and hydrides have become promising families for solid hydrogen storage due to their lightweights and favorable thermodynamic stabilities. It has been demonstrated that 6.5 wt% of hydrogen can be reversibly stored in the Li-N-H system according to this aquation:Li2NH + H2 = LiNH2 + LiH,  ΔH=-44.5 kJ/molH 2Minor amounts of aluminum chloride (0.03 mol) was added in the LiNH2-LiH system by ball-milling. The new composite formed enhances the hydrogenation/dehydrogenation kinetics and improves the stability under hydrogen cycling. Moreover, the addition of AlCl3 could suppress ammonia emission during the dehydrogenation process of the LiNH2 -LiHsample.In order to understand the role of AlCl3 addition on the Li-N-H system, the interactionsbetween the AlCl3 additive and the LiNH2-LiH system have been systematically investigated by differential scanning calorimetry, hydrogen volumetric measurements, X-ray powder diffraction, FT infrared analysis and solid-state nuclea magnetic resonance.Samples with different amount of AlCl3 were prepared by milling with the LiNH2-LiH mixture. For AlCl3 addition higher than 0.03 mol, the formation of a new amide-chloride phase is detected by XRPD and confirmed by FTIR and RMN. The present work suggests that the Li-Al-N-H-Cl phase can be produced by ball milling of LiNH2-LiH-xAlCl3 andposterior thermal heating under hydrogen. The new amide-halide phase is the responsible of the improvement in the sorption kinetics and the suppression of NH3 emission. This novel phase accelerates the migration of the ions during dehydrogenation.