高分散性金属硼氢化物超细纳米点的形成机理及其可逆储氢性能研究

The metal borohydrides nanostructures prepared by existing process usually suffer from the inevitable agglomeration, relatively larger size and broad size distribution, which make it difficult to produce dramatic size effects. To overcome it, based on our earlier work, in this project we develop the ultrafine M(BH4)n (M = Na,Ca,Mg,Y; n = 1,2,3) nanodots with excellent dispersibility supported by graphite, carbon onions or multilayered graphene via mechanical-force-induced strategy based on the coupling interactions between metal borohydrides and carbon supports. Firstly, the correlation among mechanical-force-induced preparation procedures, in situ exfoliation of carbon supports and formation of metal borohydrides nanodots is systematically explored for revealing the mechanisms and key factors of the formation of borohydrides nanodots; Secondly, the relevance of microstructural features of metal borohydrides nanodots and carbon supports with the enhanced de-/re-hydrogenation properties is ascertained carefully; Thirdly, the effect of cyclic structural evolution on the reversible hydrogen storage in metal borohydrides nanodots is deeply understood to seek new routes for further improving their performances. The results of this project have some degree of guiding significance in development of complex hydrides nanostructures with better performances for hydrogen storage.

现有工艺所制备的金属硼氢化物纳米结构易团聚、粒径相对较大且分布范围宽，难以获得显著的纳米尺寸效应来调变其固态储氢性能。为此，结合申请人的前期工作积累，本项目提出以石墨、洋葱碳或多层石墨烯为载体，借助金属硼氢化物与碳材料的内在相互作用，采用机械力诱导策略来构建高分散性M(BH4)n(M = Na,Ca,Mg,Y; n = 1,2,3)超细纳米点。拟着重探索机械力诱导制备工艺、碳载体原位解离和金属硼氢化物超细纳米点构建之间的相关性，揭示金属硼氢化物超细纳米点的形成规律，明确其关键影响因素；阐明金属硼氢化物超细纳米点和碳载体的微观结构特性与其增强脱/加氢性能之间的内在关联；在此基础上，深入理解循环组织结构演变对其可逆储氢的微观作用机制，并探索性能调变的新路径。本项目的研究结果对配位氢化物的纳米结构调制及性能改善具有一定的指导意义。

基于氢（氢化物）与材料的相互作用可实现低维纳米材料的可控制备和储氢（电）性能的有效调控。然而，上述相互作用与固态储氢和电化学性能之间的内在关联及影响机制未知。为此，本项目首先研究了石墨等纳米碳材料对硼氢化物与卤化物原位反应的影响及石墨材料的解离效应，并探究其作为固态储氢材料和锂离子负极材料的使用性能；其次，从构建界面耦合和金属电负性调控入手，有效改善Mg基体系的储氢性能；最后，系统研究了低维金属电极与硼氢化锂电解质之间的界面调控及其对全固态储锂性能的影响及作用机制。结果表明：1）借助石墨与硼氢化物相互作用，不仅实现了石墨自身的原位解理，还生成了纳米负载的金属硼氢化物；且其阳离子电负性与石墨固态解理、脱加氢/锂之间存在强关联。2）基于原位形成的Mg‒Zr‒H低能界面，有效调控Mg‒H体系的原子和电子迁移过程，实现了Mg-H体系的低温可逆储氢。3）以LiBH4固态电解质，Bi纳米片为电极来构建稳态界面，在无需经历中间相即可实现快速稳定的固态储锂。通过本项目研究，共发表SCI收录论文10篇（均标注基金号），申请发明专利2项，培养硕士研究生2人，参加国际学术会议2次，出版学术专著1部。本研究工作不仅为探索低维材料可控制备、固态储氢和电化学性能调控提供了理论依据，还将为轻金属硼氢化物基储氢材料和全固态电池的未来应用产生重要启示作用。