The investigations based on kinetic improvement and reaction mechanisms during melt infiltration, dehydrogenation, and rehydrogenation of nanoconfined 2LiBH4-MgH2-0.13TiCl4 in carbon aerogel scaffold (CAS) are proposed. It is found that TiCl4 and LiBH 4 are successfully nanoconfined in CAS, while MgH2 proceeds partially. In the same temperature (25-500 C) and time (0-5 h at constant temperature) ranges nanoconfined 2LiBH4-MgH 2-0.13TiCl4 dehydrogenates completely 99% of theoretical H2 storage capacity, while that of nanoconfined 2LiBH 4-MgH2 is only 94%. Nanoconfined 2LiBH4- MgH2-0.13TiCl4 performs three-step dehydrogenation at 140, 240, and 380 C. Onset (the first-step) dehydrogenation temperature (140 C), significantly lower than those of nanoconfined sample of 2LiBH 4-MgH2 and 2LiBH4-MgH2-TiCl 3 (ΔT = 140 and 110 C, respectively) is in agreement with the decomposition of eutectic LiBH4-Mg(BH4)2 and lithium-titanium borohydride. For the second and third steps (240 and 380 C), decompositions of LiBH4 destabilized by LiCl solvation and MgH 2 are accomplished, respectively. In conclusion, dehydrogenation products are B, Mg, LiH, and TiH. Reversibility of nanoconfined 2LiBH 4-MgH2-0.13TiCl4 sample is confirmed by the recovery of LiBH4 after rehydrogenation together with the formation of [B12H12]- derivatives. The superior kinetics during the 2nd, 3rd, and 4th cycles of nanoconfined 2LiBH4-MgH 2-0.13TiCl4 to the nanoconfined 2LiBH4-MgH 2 can be due to the formations of Ti-MgH2 alloys (Mg 0.25Ti0.75H2 and Mg6TiH2) during the 1st rehydrogenation.

2LiBH4-MgH2-0.13TiCl4 confined in nanoporous structure of carbon aerogel scaffold for reversible hydrogen storage

MILANESE, CHIARA;Ferrara C.;MARINI, AMEDEO;
2014

Abstract

The investigations based on kinetic improvement and reaction mechanisms during melt infiltration, dehydrogenation, and rehydrogenation of nanoconfined 2LiBH4-MgH2-0.13TiCl4 in carbon aerogel scaffold (CAS) are proposed. It is found that TiCl4 and LiBH 4 are successfully nanoconfined in CAS, while MgH2 proceeds partially. In the same temperature (25-500 C) and time (0-5 h at constant temperature) ranges nanoconfined 2LiBH4-MgH 2-0.13TiCl4 dehydrogenates completely 99% of theoretical H2 storage capacity, while that of nanoconfined 2LiBH 4-MgH2 is only 94%. Nanoconfined 2LiBH4- MgH2-0.13TiCl4 performs three-step dehydrogenation at 140, 240, and 380 C. Onset (the first-step) dehydrogenation temperature (140 C), significantly lower than those of nanoconfined sample of 2LiBH 4-MgH2 and 2LiBH4-MgH2-TiCl 3 (ΔT = 140 and 110 C, respectively) is in agreement with the decomposition of eutectic LiBH4-Mg(BH4)2 and lithium-titanium borohydride. For the second and third steps (240 and 380 C), decompositions of LiBH4 destabilized by LiCl solvation and MgH 2 are accomplished, respectively. In conclusion, dehydrogenation products are B, Mg, LiH, and TiH. Reversibility of nanoconfined 2LiBH 4-MgH2-0.13TiCl4 sample is confirmed by the recovery of LiBH4 after rehydrogenation together with the formation of [B12H12]- derivatives. The superior kinetics during the 2nd, 3rd, and 4th cycles of nanoconfined 2LiBH4-MgH 2-0.13TiCl4 to the nanoconfined 2LiBH4-MgH 2 can be due to the formations of Ti-MgH2 alloys (Mg 0.25Ti0.75H2 and Mg6TiH2) during the 1st rehydrogenation.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11571/992795
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