掺杂Co、Ni对LiBH_4解氢性能影响的第一原理研究

Study on First-principles of Influence of Dopants Co and Ni on Dehydrogenation Properties of LiBH_4

采用基于密度泛函理论的第一原理赝势平面波方法,计算了Co、Ni掺杂LiBH4体系的晶体与电子结构及解氢性能的影响。负合金形成热与H原子解离能的计算发现:金属元素Co、Ni在LiBH4中少量置换固溶时,体系结构稳定性发生变化,合金化增强了体系解氢能力,其中Co提高LiBH4体系解氢效果较好。电子态密度与电子密度分析发现:合金化提高LiBH4解氢能力的主要原因是Co、Ni导致LiBH4体系Fermi能级附近能隙减小,BH键的键长增长和重叠布局数减小及Li与BH之间的成键作用减弱。

The crystal, electronic structure and dehydrogenating of Co and Ni for LiBH4 system were calculated by first-principles based on density functional theory. The calculated negative heat of formation and dissociation energy of H atom show that when a little Co and Ni dissolve into LiBH4 in a small amount of replacement solution, there are some changes on structural stability. Alloying elements can improve the dehydrogenating properties of the system. After analyzing the density of states （DOS） and charge distribution, it is found that the catalysis effect of Co and Ni on the dehydrogenating kinetics of LiBH4 may attribute to the reduction of energy gap near Fermi level, the growth of bonding length and the reductions of overlap population with BH bonding and the weakened bonding between Li and BH.