Improved thermolytic dehydrogenation of LiBH4 nanoconfined in few-layer graphene with different functionalities

Abstract

In this work, lithium borohydride (LiBH4) was loaded into plasma-activated nanoporous few-layer graphene (FLG) powders with different specific surface areas (∼400–800 m2/g) and functional groups (carboxyl and amine) to investigate the effect of LiBH4@FLG nanoconfinement on the dehydrogenation properties. It was observed that the dehydrogenation temperature dropped significantly from 463 °C for pure LiBH4 to ∼120 °C for all LiBH4@FLG nanocomposites. This was attributed to the nano-sized pores of the FLG materials that can constrain LiBH4 by nanoconfinement and thus decrease the dehydrogenation temperature. The highest dehydrogenation yield of 83% occurred in LiBH4@FLG with 400 m2/g surface area and amine groups, possibly due to Lewis basic amino groups and better graphitic structure. Moreover, it was found that both the surface area and the graphitic defects on the FLG host materials have an influence on the dehydrogenation kinetics. LiBH4@FLG with 800 m2/g surface area and carboxyl groups possesses the lowest activation energy due to its high surface area and high concentration of graphitic defects.