Improved hydrogen storage properties of NaAlH4[sbnd]MgH2[sbnd]LiBH4 ternary-hydride system catalyzed by TiF3

Abstract

In this study, the hydrogen storage properties and reaction mechanisms of a NaAlH4MgH2LiBH4 destabilized system with a TiF3 additive are investigated for the first time. It was found that the addition of TiF3 resulted in both decreased decomposition temperature and improved sorption kinetics compared with that of un-doped NaAlH4MgH2LiBH4. The onset dehydrogenation temperature for all stages in the TiF3-doped composite was reduced by 100 °C, 30 °C and 20 °C compared with the un-doped composite. For the rehydrogenation kinetics, the TiF3-added sample absorbed ∼4.5 wt.% hydrogen at 350 °C after 30 min of rehydrogenation; however, the un-doped composite only absorbed ∼3.5 wt.% hydrogen. Differential scanning calorimetry indicated that the number of thermal events in the NaAlH4MgH2LiBH4 composite reduced from six to four after doping with TiF3. It is believed that the formation of Ti- and F-containing species during ball milling or dehydrogenation may be responsible for the catalytic effects, further improving the hydrogen storage properties of the TiF3-doped NaAlH4MgH2LiBH4 composite system.