Direct rehydrogenation of LiBH4 from H-deficient Li2 B12 H12−x

Abstract

Li2 B12 H12 is commonly considered as a boron sink hindering the reversible hydrogen sorption of LiBH4. Recently, in the dehydrogenation process of LiBH4 an amorphous H-deficient Li2 B12 H12−x phase was observed. In the present study, we investigate the rehydrogenation properties of Li2 B12 H12−x to form LiBH4. With addition of nanostructured cobalt boride in a 1:1 mass ratio, the rehydrogenation properties of Li2 B12 H12−x are improved, where LiBH4 forms under milder conditions (e.g., 400◦ C, 100 bar H2) with a yield of 68%. The active catalytic species in the reversible sorption reaction is suggested to be nonmetallic Cox B (x = 1) based on11 B MAS NMR experiments and its role has been discussed.