In situ synchrotron radiation powder X-ray diffraction study of the 2LiNH2 + LiH + KBH4 system

• Experimental study of the desorption mechanism of 2LiNH2 + KBH4 + LiH system by in situ synchrotron radiation powder X-ray diffraction was performed.
• The formation of Li3BN2 and KH expected in the theoretical study was supported by experimental evidences.
• Full desorption of the ternary system was achieved at 400 °C.
• Desorption process of 2LiNH2 + KBH4 LiH was performed by in situ SRPX diffraction.
• The formation of Li3BN2 and KH was supported by experimental evidences.Full desorption of the ternary system was achieved at 400 °C.

In the present work we focus on the 2LiNH2 + KBH4 + LiH system: the phase-structural transformations occurring during the desorption process on the powder mixture are described by in situ synchrotron radiation powder X-ray diffraction (SR-PXD), high-pressure differential scanning calorimetry and manometric measurements. It is observed that LiNH2 transforms into Li2NH during heating, at about 160 °C, while the reflections related to KBH4 disappeared at 380 °C. At higher temperature, the formation of Li3BN2 is detected, together with an evident increase of the background, ascribable to the presence of a further phase in the molten state. Patterns at room temperature, after cooling down the sample, confirm the presence of Li3BN2 and KH as reported in the theoretical study. For the as prepared mixture it is possible to achieve the theoretical hydrogen gravimetric capacity of 7.4 wt%.