中文摘要：

应用基于密度泛函理论的第一性原理方法,研究了TiF3, TiCl3催化剂中阴阳离子对LiBH4的协同催化机理。研究发现：金属Ti相对于卤族元素掺杂不容易实现；金属和卤族元素同时掺杂比Ti单独掺杂容易实现；对TiF3催化剂,一种元素掺杂的实现有助于另一种元素掺杂的实现,这大大提高了掺杂浓度。基于电子结构分析,得出卤族元素单独掺杂会降低LiBH4的稳定性； Ti单独掺杂使LiBH4费米能级升高、在带隙中引入缺陷能级、使B—H键结合减弱,这些可能是Ti的卤化物催化剂大大改善LiBH4释氢性能的原因。 LiBH4中加入Ti的卤化物催化剂改善其释氢性能主要是由于催化剂使B—H共价结合减弱,这使得氢容易扩散。 TiF3, TiCl3催化剂,在LiBH4可逆释氢反应过程中F, Ti协同降低B—H共价结合,而Cl, Ti这种协同作用不显著,这是TiF3对LiBH4催化效果优于TiCl3的原因。

英文摘要：

The synergistic catalytic mechanism of anion, cation ions in TiF3, TiCl3 catalysts for LiBH4 has been studied by first-principles method based on density functional theory. According to the results, Ti metal doping in LiBH4 is not easy realized with respect to halogen elements. Co-doping with transition metal and elements in halogen family is achieved easier than doping with Ti alone. For TiF3 catalyst, to achieve doping with one kind of element is helpful to doping with another kind of element, which accordingly results in the increase of doping concentration. Based on the analysis of the electronic structure, we find that doping with halogen element alone can reduce the stability of LiBH4; while doping with Ti alone leads to the rise of Fermi level; the introduction of defect energy level and the weakening of B–H bond;these may be responsible for improving greatly the desorption kinetics of LiBH4 by titanium halide catalysts. The improvement of the dehydrogenating kinetics of LiBH4 with titanium halide catalyst additives is mainly due to the B–H bond weakening, which makes H atom diffuse easily. For TiF3, TiCl3 catalysts, in the reversible desorption process of LiBH4, F and Ti have synergistic action for the B–H bond weakening, but the synergistic action of Cl and Ti is not obvious, this may be the reason for the advantage of TiF3 over TiCl3 in LiBH4 catalytic reaction.