Promoted dehydrogenation in ammine lithium borohydride supported by carbon nanotubes

摘要

In this paper, ammine lithium borohydride (LiBH_4·NH _3) was successfully impregnated into multi-walled carbon nanotubes (CNTs) through a melting technique. X-ray diffraction, scanning electron microscopy, Brunauer-Emmett-Teller, and density measurements were employed to confirm the formation of the nanostructured LiBH_4·NH _3/CNTs composites. As a consequence, it was found that the dehydrogenation of the loaded LiBH_4·NH_3 was remarkably enhanced, showing an onset dehydrogenation at temperatures below 100 °C, together with a prominent desorption of pure hydrogen at around 280 °C, with a capacity as high as 6.7 wt.%, while only a trace of H_2 liberation was present for the pristine LiBH_4·NH_3 in the same temperature range. Structural examination indicated that the significant modification of the thermal decomposition route of LiBH _4·NH_3 achieved in the present study is due to the CNT-assisted formation of B-N-based hydride composite, starting at a temperature below 100 °C. It is demonstrated that the formation of this B-N-based hydride covalently stabilized the [NH] groups that were weakly coordinated on Li cations in the pristine LiBH_4·NH_3via strong B-N bonds, and furthermore, accounted for the substantial hydrogen desorption at higher temperatures.