耦合增强轻金属/稀土金属配位硼氢化物的储氢特性

To overcome the drawbacks of high thermal stability and poor reversibility of metals complex borohydrides-based hydrogen storage materials, based on our earlier work, in this project we develop a coupled system including light metal and rare-earth metal complex borohydrides for improving reversible hydrogen storage properties via the coupling interactions between these components. Firstly, the correlation among components, thermostability and hydrogen storage properties of xM(BH4)n-(1-x) Re(BH4)n(M = Li, Na, Mg; Re = Sc, Y; 0<x<1; n is stoichiometric number) composites is systematically investigated from a thermodynamics point of view; Secondly, the evolution of the de-/re-hydrogenation pathway is revealed carefully; Thirdly, the mechanism of hydrogen storage properties improved by the coupling interactions are deeply understood. Based on the obove results, the effects of adding hydrides and nanoconfinment on both the coupling interactions and hydrogen storage properties of these composites are studied for further improving their performances. The results of this project have some degree of guiding significance in development of high performance complex hydrides-based hydrogen storage materials.

针对金属配位硼氢化物储氢材料存在的热稳定性高及可逆性能差的问题，结合申请人的前期工作积累，本项目提出了构建轻金属/稀土金属配位硼氢化物双相耦合体系，利用组元之间的耦合增强效应，以降低热稳定性及改善可逆储氢性能。拟从热力学角度系统研究xM(BH4)n-(1-x)Re(BH4)n(M = Li,Na,Mg；Re = Sc,Y；0<x<1；n为化学计量数)复合体系的组分、热稳定性与储氢性能的相关性，揭示复合体系脱/加氢反应路径的演变规律，阐明可逆储氢性能的耦合调控机制；在此基础上，进一步探索氢化物添加和纳米限域对轻金属/稀土金属配位硼氢化合物复合体系耦合行为和储氢性能的影响规律，以提高其综合储氢性能。本项目的研究结果对研发高性能配位氢化物储氢材料具有一定的指导意义。

本项目首先采用挥发诱导自组装和直接机械力化学工艺可控制备了多种轻金属硼氢化物纳米结构，并揭示了其形成机制及增强储氢性能；为了避免颗粒团聚，进一步借助与碳材料的内在耦合作用构建了高分散性轻金属硼氢化物超细纳米点，以显著提升其循环性能；其次查明了双金属氢化物的动力学衰退机制，提出了原位激活策略来改善其吸/放氢性能；最后系统研究了原位形成的稀土金属氢化物与轻金属硼氢化物的耦合增强储氢性能。研究结果表明：1）可控合成出不同形貌的、能空气中稳定存在的LiBH4、NaBH4和Ca(BH4)2纳米结构，发现LiBH4脱氢性能与其纳米颗粒尺寸密切相关；2）原位嵌入石墨纳米片层形成6 nm左右的NaBH4纳米点，实现其~250 °C低温放氢；3）原位引入YH3和Ni纳米粒子可有效抑制NaMgH3的相分离现象，并显著增强其循环动力学性能；4）MClx (M = Ce, Y)与LiBH4原位耦合实现了300 °C以下快速放氢，远低于纯LIBH4的放氢温度。通过本项目工作，发表SCI收录论文6篇，申请/授权国家发明专利3项，培养硕士研究生3人。本研究工作不仅为探索高容量硼氢化物储氢材料提供了理论依据，还为后续实际应用打下了基础。