Effects of Ti and Nb on hydrogen desorption of Mg(BH₄)₂

Abstract

In this work, the effects of catalysts (Ti, TiO2, TiCl3, Nb2O5, and NbCl5) were investigated on hydrogen desorption of Mg (BH4)2. LiBH4 and MgCl2 with a 2:1 molar ratio were mixed by ball milling to prepare Mg (BH4)2. The desorption behaviors were measured by a thermo-volumetric apparatus from room temperature to 450 °C with a heating rate of 2 °C/min. The hydrogen desorption capacity of the mixed sample milled for 2 h was 4.78 wt.% with a 2-step release. The first step occurred at 214 °C, and the second step appeared at 374 °C. The addition of 16 wt.% catalysts decreased the desorption temperature in the second step by 70 °C except for the Ti catalyst. The addition of Nb205 and TiO2 also decreased the desorption temperature in the second step by 70 °C, and the hydrogen desorption capacity to 4.86 wt.% and 5.27 wt.%, respectively. Furthermore, effects of Nb2O5 and TiO2 loading (10 wt.%, 16 wt.%, and 20 wt.%) were investigated. The results showed that 16 wt.% loading exhibited the best performance among all tested catalysts. Hydrogen absorption after desorption of Mg (BH4)2 was also studied under 9.5 MPa and 350 °C for 12 h.