Enhanced hydrogen storage capacity and reversibility of LiBH4 encapsulated in carbon nanocages

In this work, we first obtained carbon nanocages (CNCs) with nanoporous structure and high specific surface area via a template synthesis method, and then prepared a LiBH4@CNCs hydrogen storage composite by combining melting LiBH4 into the CNCs. Temperature programmed desorption (TPD) analyses show that the composite starts to release hydrogen at 200 °C, with the maximal desorption peak occurs at about 320 °C, which is 180 °C lower than that of the pure LiBH4. Also, the final hydrogen desorption capacity reaches 7.5 wt.%. We also see enhanced reversible properties of the composite, of which 78% initial hydrogen is absorbed after five de/rehydrogenation cycles at 400 °C. The further studies show that the LiBH4 can react with the oxygen-containing group of CNCs to form LiBO2 during the infiltration process. The LiBO2 dispersed on the scaffold of CNCs further reacts with LiBH4 to release more hydrogen, and the reaction product Li3BO3 as an efficient catalyst can significantly improve the reversible hydrogen storage properties of the LiBH4. The synergetic effect of nanoconfinement of CNCs and catalysis of Li3BO3 is proved to be largely beneficial for the decomposition process and reversible hydrogen absorption of LiBH4.