钾（铷）基三元过渡金属氢化物对氨基镁-氢化锂体系储氢性能的影响及其作用机理的研究

储氢是制约氢能大规模利用的技术瓶颈之一。氨基镁-氢化锂（Mg(NH2)2-2LiH）储氢体系，因具有温和的脱氢焓值（~ 40.0 kJ/(mol-H2)）和较高的循环储氢容量（5.6 %重量比）而备受关注。该体系存在的主要问题是吸脱氢速度缓慢。前期研究主要集中在用KH或RbH修饰此体系的热力学和动力学性能。申请者近期的研究工作发现钾（铷）基三元过渡金属氢化物（如K3ZnH5等）修饰的LiNH2-LiH体系加氢动力学有大幅度的提升，在1分钟内其加氢程度可高达70%。受此启发，本项目拟考察钾（铷）基三元过渡金属氢化物对Mg(NH2)2-2LiH体系吸脱氢动力学性能的影响。借助钾（铷）和过渡金属的协同作用，使得Mg(NH2)2-2LiH的吸脱氢速率进一步提升以期满足实际应用需求。此外，钾（铷）基三元过渡金属氢化物的作用机制将借助同步辐射原位X-射线衍射（吸收）和原位红外等表征手段得以阐明。

Mg(NH2)2-2LiH composite is a promising hydrogen storage material due to its relatively high reversible hydrogen capacity (∼ 5.6 wt %) and suitable thermodynamic properties (∆H ≈ 40.0 kJ/(mol-H2)) that allow hydrogen sorption conducting at temperatures below 90 °C. However, the presence of severe kinetic barriers inhibit its low-temperature operation. So far, KH(RbH) is one of the best kinetic additives for Mg(NH2)2-2LiH, and the additive effect of KH(RbH) in Mg(NH2)2-2LiH attracts increasing interest in recent. Last year, ternary transition hydrides such as K3ZnH5, Rb3ZnH5, Rb3MnH5, have been used as additives for LiNH2-LiH system. The doped samples can absorb more than 70% of H2 within 1 min at ca. 190 °C and 50 bar of H2, this is, to the best of our knowledge, the fastest absorption rate observed in amide-hydride systems to date. Inspired by this, K(Rb)-based ternary transition hydrides will be chosen as additives for Mg(NH2)2-2LiH. In hope that with the synergic effect of K(Rb)H and transition metals improves the kinetics of Mg(NH2)2-2LiH. Additionally, reaction mechanism of the doped Mg(NH2)2-2LiH will be systematically investigated by in situ synchrotron radiation powder X-ray radiation diffraction and absorption techniques and in situ infrared spectra. The intermediate phases will be resolved by Rietveld approach. Understanding on the structural transformation following de/re-hydrogenation will lead us to the identification of kinetic barriers, whilst, sheds some light on kinetics improvement of amide-hydride composites.