轻金属配位氢化物中的催化机理及新催化结构探索的理论研究

It has attracted intensive attention in the field of renewable energy materials to catalytically enhance the hydrogen storage properties of light metal complex hydrides. The extensive experimental studies call for detailed theoretical studies on the mechanism. With the aim to study the "catalytic mechanism" and the "new nano catalyst structure" fundamental important topics of this field, we would like to use the first-principles method and the improved nudged elastic band technique to focus on the following studies: (a) The detailed reaction path catalyzed by the transition metal, anion dopant, or metal oxide nanostructure would be investigated. Combining the analysis on geometrical and electronic properties, we would conclude the catalytic mechanism for improving the hydrogen storage ability; (b) As to the supported or nanoconfined light metal complex hydride nanomaterials, we would concentrate on checking the relationship between the size and the hydrogen storage properties, the effects from the supporting materials and the inner wall of the porous materials; (c) With the purpose to predict new nano catalysts for the light metal complex hydrides on theory, we would perform detailed investigations on the geometrical structures of the co-doped catalysts and their catalytic performance, the catalytic properties of the previously reported metal oxide nanostructures such as the nanotube and nanowire, and the catalytic applications of the two-dimensional materials. In summary, we would concentrate on studying the reaction path and the corresponding mechanism on one hand and designing new nano catalyst materials on the other hand based on our detailed studies of the catalytic reaction pathway, the structural and electronic properties on the atomic level. These studies can provide valuable theoretical results to the new materials design and to some sense can provide predictions or guide the corresponding experimental studies, which would in turn benefit the renewable energy materials design and application studies.

催化改善轻金属配位氢化物的储氢性能是新能源领域的重要研究方向，广泛的实验探索对其催化机理的理论研究提出了迫切要求。围绕"催化机理"和"新纳米催化结构"基础课题，我们主要采用第一性原理方法和改进的Nudged Elastic Band Method技术研究：①过渡金属、阴离子、金属氧化物纳米结构催化的反应路径及相应的几何和电子性质研究，阐述催化机理；②针对纳米限域及载体支撑氢化物的研究进展，研究小尺寸效应、接触面对储氢性能的载体效应等；③探索催化成份的混合共存形式及其协同催化性质、纳米管或线等已报道的金属氧化物纳米结构的催化性质、二维材料的催化性质，从理论上为轻金属氢化物预测新催化结构。在详细研究催化反应路径、几何和电子性质基础上，以"催化机理"研究为特色，以"新纳米催化结构"探索为创新，实现原子层次上阐述机理并预测新材料的目的，为实验研究提供理论借鉴，促进新能源材料的设计开发和应用研究。

通过第一性原理计算和最佳反应路径搜索，研究了过渡金属催化成份在轻金属配位氢化物催化中的反应机理以及金属配位氢化物中的原子扩散问题，已经取得的主要理论成果有：完整铝表面上的最上层中，催化成份通过Kubas型贡献-反贡献电子机制，建立弱化学相互作用，激活并分解氢分子，缺点是裸露的催化成份容易被氢原子包围导致催化成份中毒失效；催化成份在次上层时，通过局部结构畸变、贡献价电子能力等影响其上层的铝原子，改变其反应活性，催化激活并分解氢分子，同时由于铝的屏蔽，氢原子可以快速扩散，缺点是催化成份的催化能力不同程度的降低，可以通过原子半径和催化成份的电子负电性进行初步筛选合适的催化成份；当催化成份位于台阶下沿时，可以有效结合两种催化机制的优点，获得最优的催化反应活性和氢原子扩散性能，综合催化性能表现较好；次近邻掺杂替代情况下，以Ti为例研究的同质掺杂域中，存在协同催化增强作用，异质掺杂域中增强效应不明显，更多异质掺杂情况有待进一步探索；多孔材料共价有机框架结构中，获得了通过桥接改变界面影响提升催化性能的理论成果，对气体分子水合物多孔材料研究中获得了小分子共存增强稳定性等理论结论；另外，在课题支持下，以硕士研究生为主，还扩展了研究方向，首先解释了课题研究过程中发现的二维材料能带工程疑惑，通过分析价键对称性破缺解释了具有反演对称性的二维超晶格中的能带工程现象，其次通过全局搜索预测了若干新型二维材料结构，如具有门电压调控自旋过滤性能的三明治结构MnB6二维结构。