元素掺杂对VH_2解氢性能的影响

Influence of dopants on the dehydrogenation properties of VH_2

采用密度泛函理论(DFT)的第一性原理的平面波超软赝势方法,研究了Zr、Cu、Zn掺杂对VH2的电子结构和解氢性能的影响.计算结果显示Zr掺杂VH2后晶体模型的负合金形成热增加和费米能级Ef处电子浓度N(Ef)的减少,体系结构稳定性增强;V–H之间重叠集居数和电子密度计算也显示V–H之间相互作用增强;表明在VH2中掺杂Zr以后吸放氢最大容量增加,但解氢能力减弱.而Cu或Zn掺杂VH2以后晶体模型的负合金形成热减少和费米能级Ef处电子浓度N(Ef)的增加,体系结构稳定性减弱;V–H之间重叠集居数和电子密度计算也显示V–H之间相互作用减弱;表明在VH2中掺杂Cu或Zn以后吸放氢最大容量降低,但解氢能力增强.与实验结论相符.同时Mulliken集居数计算结果还显示V-d轨道Mulliken集居数与掺杂有关,掺杂Zr以后V-d轨道Mulliken集居数减少;掺杂Cu或Zn以后V-d轨道Mulliken集居数增加.

Using the plane waves ultrasoft pseudopotential method based on the first principles of DFT, the influence of doping Zr, Cu and Zn on the electronic structure and dehydrogenation properties of VH2 was studied. The results show that the negative formation heat increases and the valence electron number at EF, N（Ef） decreases in doping Zr model, indicating higher stability of VH2 model by Zr alloying. On the other hand, the negative formation heat of VH2 decreases and the N（Ef） increases in doping Cu or Zn system, suggesting lower stability of VH2 model by Cu or Zn alloying. The calculated results of overlap population and electron density of V-H bond demonstrate that the interaction of V-H bond is strengthened by Zr alloying and weakened by Cu or Zn alloying. So we can conclude that the maximum capacity of absorbing and desorbing hydrogen can be raised by introduction of Zr and reduced by introduction of Cu or Zn, while the dehydrogenation property would be lower in Zr alloying model and improved in Cu or Zn alloying system. And these are consistent with experimental results. Furthermore, Mulliken populations are also calculated and it is found that the Mulliken population of V-d orbital decreases by Zr doping and increases by Cu or Zn doping.