Effects of fluoride additives on dehydrogenation behaviors of 2LiBH4 + MgH2 system

Various additives such as NbF5, TiF3, CeF3, LaF3 and FeF3 were used to dope 2LiBH4 + MgH2 system and their dehydriding properties were investigated systematically. Among the different additives, NbF5 exhibited the most prominent behavior in terms of fast kinetics and lower the dehydrogenation temperature of 2LiBH4 + MgH2 system. Differential scanning calorimetry (DSC) shows that 2LiBH4 + MgH2 system milled with 5 mol% NbF5 lowered the dehydrogenation temperature by 30 °C and 58 °C for the two-step dehydrogenation compared to neat 2LiBH4 + MgH2 system. Temperature programmed desorption (TPD) indicates that 2LiBH4 + MgH2 + 0.05NbF5 dehydrided completely below 450 °C with 8.1 wt.% hydrogen released. Fourier transform infrared spectrometer (FTIR) and X-ray diffraction (XRD) analysis evidence that MgB2 was fully formed after dehydrogenation. Experimental results show that the 2LiBH4 + MgH2 + 0.05NbF5 system indeed has good reversible hydriding/dehydriding properties.