Mechanistic investigations on significantly improved hydrogen storage performance of the Ca(BH4)2-added 2LiNH2/MgH2 system

• Published in: International journal of hydrogen energy 2013-04, Vol.38 (12), p.5030-5038
• Main Authors: Li, Bo, Liu, Yongfeng, Gu, Jian, Gu, Yingjie, Gao, Mingxia, Pan, Hongge
• Format: Article
• Language: English
• Subjects: Alternative fuels. Production and utilization; Amide; Applied sciences; Borohydrides; Energy; Exact sciences and technology; Fuels; Hydrogen; Hydrogen storage; Kinetics; Mechanisms
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2013.02.011

The hydrogen storage properties and mechanisms of the Ca(BH4)2-added 2LiNH2–MgH2 system were systematically investigated. The results showed that the addition of Ca(BH4)2 pronouncedly improved hydrogen storage properties of the 2LiNH2–MgH2 system. The onset temperature for dehydrogenation of the 2LiNH2–MgH2–0.3Ca(BH4)2 sample is only 80 °C, a ca. 40 °C decline with respect to the pristine sample. Further hydrogenation examination indicated that the dehydrogenated 2LiNH2–MgH2–0.1Ca(BH4)2 sample could absorb ca. 4.7 wt% of hydrogen at 160 °C and 100 atm while only 0.8 wt% of hydrogen was recharged into the dehydrogenated pristine sample under the same conditions. Structural analyses revealed that during ball milling, a metathesis reaction between Ca(BH4)2 and LiNH2 firstly occurred to convert to Ca(NH2)2 and LiBH4, and then, the newly developed LiBH4 reacted with LiNH2 to form Li4(BH4)(NH2)3. Upon heating, the in situ formed Ca(NH2)2 and Li4(BH4)(NH2)3 work together to significantly decrease the operating temperatures for hydrogen storage in the Ca(BH4)2-added 2LiNH2–MgH2 system. ► Hydrogen storage properties of 2LiNH2–MgH2 are improved by doping Ca(BH4)2. ► Hydrogen desorption from the 0.3Ca(BH4)2-doped sample starts at 80 °C. ► Ca(BH4)2 reacts with LiNH2 to form Ca(NH2)2 and LiBH4 during ball milling. ► The newly formed Ca(NH2)2 and LiBH4 provide the synergetic effects.