Hydrogen Storage Properties of Nanoconfined LiBH₄–Mg₂NiH₄ Reactive Hydride Composites

LiBH 4 –Mg 2 NiH 4 reactive hydride composites have been nanoconfined into two types of mesoporous carbons: a templated carbon with ordered small pores of ∼4 nm and a carbon aerogel with pores size of ∼30 nm. In situ synchrotron X-ray diffraction has revealed the formation of the MgNi 2.5 B 2 compound during dehydrogenation at 300 °C and 5 bar of H 2 pressure. The hydrogen desorption from nanoconfined LiBH 4 –Mg 2 NiH 4 shows a single-step reaction at around 300 °C, as observed by mass spectroscopy coupled with thermogravimetric analysis. A synergistic effect is suggested, which facilitates lower hydrogen release than previously reported nanoconfined systems. Effective nanoconfinement provides faster kinetics of hydrogen release. Nevertheless, LiBH 4 –Mg 2 NiH 4 shows progressive loss of capacity during cycling.