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

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.