A comparative study of the hydrogen storage properties of LiBH4 doping with CaHCl and CaH2

In the present work, CaHCl was synthesized as an additive for the LiBH4 complex hydride. The hydrogen storage properties of LiBH4 doping with CaHCl was firstly investigated and compared to LiBH4 doping with CaH2. It is found that LiBH4 doping with CaHCl exhibits more promising catalytic properties than that of CaH2: doping with CaHCl can decrease the thermodynamic stability of LiBH4 and improve the low temperature dehydrogenation kinetics of LiBH4 greater than CaH2 do. The activation energy of the dehydriding step of LiBH4 decreases from 160.11 kJ/mol in 6LiBH4 + CaH2 system to 112.39 kJ/mol in 6LiBH4 + CaHCl system. The dehydrogenation scheme of 6LiBH4 + CaHCl system is different from 6LiBH4 + CaH2 system, and its dehydrogenation reaction is 6LiBH4 + CaHCl → 5LiH + LiCl + CaB6 + 10H2↑. However, due to the stable LiCl formed after dehydrogenation, the rehydrogenation route of 6LiBH4 + CaHCl system is the same as 6LiBH4 + CaH2 system to regenerate LiBH4 and CaH2 (in molar ratio of 6:1), which indicates that 6LiBH4 + CaHCl system cannot be fully rehydrogenated. It is also observed that 6LiBH4 + CaHCl system has more stable cyclic dehydrogenation properties than 6LiBH4 + CaH2 system.

► CaHCl exhibits more promising catalytic properties than CaH2 to LiBH4.
► CaHCl doping decrease the dehydrogenation activation energy of LiBH4 to 112.4 kJ/mol.
► The de/rehydrogenation schemes of 6LiBH4 + CaHCl were investigated in detail.
► 6LiBH4 + CaHCl system has certain stable cyclic dehydrogenation properties.