The reactions in LiBH4–NaNH2 hydrogen storage system

Publication year: 2011
Source: International Journal of Hydrogen Energy, In Press, Corrected Proof, Available online 14 June 2011

Yao, Zhang , Qifeng, Tian

Stepwise reactions were observed in the ball milling and heating process of the LiBH4–NaNH2 system by means of X-ray diffraction (XRD) and Fourier transform infrared spectrometry (FT-IR). During the ball milling process, two concurrent reactions take place in the mixture: 3LiBH4+4NaNH2→Li3Na(NH2)4 + 3NaBH4 and LiBH4 + NaNH2→LiNH2 + NaBH4. The heating process from 50 °C to 400 °C is mainly the concurrent reactions of Li3Na(NH2)4 + 3LiBH4→2Li3BN2 + NaBH4 + 8H2 and 2LiNH2 + LiBH4→Li3BN2H8→Li3BN2 + 4H2, where the intermediate phases Li3Na(NH2)4 and LiNH2 serve as the reagents to decompose LiBH4. The merged equations for the mechanochemical and the heating reactions below 400 °C can be denoted as 3LiBH4+2NaNH2→Li3BN2+2NaBH4+4H2. The maximum dehydrogenation capacity in closed system below 400 °C…

 Highlights: ► Dehydrogenation in the LiBH4–NaNH2 starts from 50 °C. ► The intermediate phases Li3Na(NH2)4 and LiNH2 during heating process serve as the reagents to decompose LiBH4. ► The maximum dehydrogenation capacity in closed system below 400 °C is 5.1 wt.% H2. ► The apparent activation energies of the two steps (114.8 and 123.5 kJ/mol) are all lower than that of bulk LiBH4.