Jianmei Huang

Ammonia borane modified zirconium borohydride octaammoniate with enhanced dehydrogenation properties

A new complex system, Zr(BH4)4·8NH3–nNH3BH3 (n = 2, 3, 4, 5), was prepared via ball milling of Zr(BH4)4·8NH3 and NH3BH3 (AB). The combination strategy effectively suppressed ammonia release and reduced the dehydrogenation temperature when compared to the individual compounds. In the optimized composition, Zr(BH4)4·8NH3–4AB, the hydrogen purity was improved to 96.1 mol% and 7.0 wt% of hydrogen was released at 100 °C. These remarkable improvements are attributed to the interaction between AB and the NH3 group in Zr(BH4)4·8NH3, which enables a more active interaction of Hδ+⋯−δH. These advanced dehydrogenation properties suggest that Zr(BH4)4·8NH3–4AB is a promising candidate for potential hydrogen storage applications.

Metal‐Borohydride‐Modified Zr(BH4)4⋅8 NH3: Low‐Temperature Dehydrogenation Yielding Highly Pure Hydrogen

Due to its high hydrogen density (14.8 wt %) and low dehydrogenation peak temperature (130 °C), Zr(BH4 )4 ⋅8 NH3 is considered to be one of the most promising hydrogen-storage materials. To further decrease its dehydrogenation temperature and suppress its ammonia release, a strategy of introducing LiBH4 and Mg(BH4 )2 was applied to this system. Zr(BH4 )4 ⋅8 NH3 -4u2009LiBH4 and Zr(BH4 )4 ⋅8 NH3 -2 Mg(BH4 )2 composites showed main dehydrogenation peaks centered at 81 and 106 °C as well as high hydrogen purities of 99.3 and 99.8 molu2009% H2 , respectively. Isothermal measurements showed that 6.6 wt % (within 60 min) and 5.5 wt % (within 360 min) of hydrogen were released at 100 °C from Zr(BH4 )4 ⋅8 NH3 -4u2009LiBH4 and Zr(BH4 )4 ⋅8 NH3 -2 Mg(BH4 )2 , respectively. The lower dehydrogenation temperatures and improved hydrogen purities could be attributed to the formation of the diammoniate of diborane for Zr(BH4 )4 ⋅8 NH3 -4u2009LiBH4 , and the partial transfer of NH3 groups from Zr(BH4 )4 ⋅8 NH3 to Mg(BH4 )2 for Zr(BH4 )4 ⋅8 NH3 -2 Mg(BH4 )2 , which result in balanced numbers of BH4 and NH3 groups and a more active H(δ+) ⋅⋅⋅(-δ) H interaction. These advanced dehydrogenation properties make these two composites promising candidates as hydrogen-storage materials.