Enhanced hydrogen storage performances of NaBH4–MgH2 system

Abstract The hydrogen storage properties of 2NaBH 4  + MgH 2 system were studied. It was found that the presence of MgH 2 could destabilize the decomposition of NaBH 4 , decreasing the dehydrogenation temperature about 40 °C compared with the pure NaBH 4 . It is believed that the formation of MgB 2 upon dehydrogenation stabilizes the dehydrogenated state and, thereby, destabilizes the NaBH 4 . For the desorption the following two-step reaction was observed: 2NaBH 4  + MgH 2  → 2NaBH 4  + Mg + H 2  → 2NaH + MgB 2  + 4H 2 . Furthermore, various catalysts such as TiF 3 , TiO 2 , Zr, Si and BCC alloy were doped to the NaBH 4 –MgH 2 system. Among these catalysts, TiF 3 exhibited the optimum behavior in terms of fast kinetics and lowering the dehydrogenation temperature of the NaBH 4 –MgH 2 system. The rehydrogenation experiments of TiF 3 -doped NaBH 4 –MgH 2 system were investigated at 600 °C with an initial hydrogen pressure of about 4 MPa. It showed that 5.89 wt.% hydrogen was rehydrogenated within 12 h. XRD results demonstrated the formation of NaBH 4 and MgH 2 in the rehydrogenated sample.