Enhanced hydrogen storage properties of 2LiBH4-LiAlH4 nanoconfined in resorcinol formaldehyde carbon aerogel

Abstract

Resorcinol formaldehyde carbon aerogel (RFC)was synthesized in this paper to be used as a scaffold for nanoconfining 2LiBH4-LiAlH4composite. LiBH4 and LiAlH4 were nanoconfined into the pores of the prepared resorcinol formaldehyde carbon aerogel by a two-step melt-infiltration process. The microstructure evolution was investigated by XRD, FTIR analysis, and BET measurements. The hydrogen storage properties were studied by TPD, TG/DSC/MS measurements. The experimental results show that LiBH4 and LiAlH4 are well dispersed in the scaffold after the melt infiltration process. The nano-confined 2LiBH4-LiAlH4 composite (denoted as 2LiBH4-LiAlH4/RFC) shows a two-step dehydrogenation process. The onset dehydrogenation temperatures for the two steps are 100 °C and 280 °C, respectively, which are 70 °C and 170 °C lower than that of the milled 2LiBH4-LiAlH4 mixture. The formation of AlB2 during the second dehydrogenation step alters the reaction pathway of LiBH4. The kinetic properties of the composite are greatly enhanced compared to the physical mixture of LiBH4 and LiAlH4. The nanoconfinement and the formation of AlB2 have a combined effect on the improvement of hydrogen storage properties for nanoconfined 2LiBH4-LiAlH4/RFC. It could be rehydrogenated at 350 °C and 5 MPa H2. A reversible hydrogen storage capacity of 5.7 wt.% is achieved.