碳硼富勒烯衍生物C18B2M(M=Li,Ti, Fe)的储氢性能计算研究

本文使用密度泛函理论(density functional theory, DFT)中的广义梯度近似(generalized gradient approximation, GGA)研究了经碱金属原子Li、过渡金属原子Ti和Fe原子修饰的富勒烯C₁₈B₂M(M=Li, Ti, Fe)的储氢性能. 研究发现, C₁₈B₂由于B的替代掺杂, 比C₂₀对金属原子具有更高的结合能. 由平均吸附能分析可知: C₁₈B₂Li对H₂的吸附能力较弱, C₁₈B₂Fe对H₂的吸附能力过强, 而C₁₈B₂Ti对H₂的平均吸附能介于0.45-0.59 eV 之间, 介于物理吸附和化学吸附之间 (0.2-0.6 eV), 因此可以实现常温下的可逆储氢. C₁₈B₂M(M=Li, Ti, Fe)能够吸附的H₂数目最多分别为4, 6和4. 由储氢机理分析可知: C₁₈B₂Li主要通过碱金属离子激发的静电场来吸附H₂, 而C₁₈B₂Ti和C₁₈B₂Fe主要通过金属原子与H₂之间的Kubas作用来吸附H₂. 由于C₁₈B₂Ti既有较大的储氢数目, 又可以实现可逆储氢, 因此有望开发成新型纳米储氢材料.

Calculations of the hydrogen storage of the boron carbon Fullerefle C18B2M(M=Li,Ti, Fe)

The generalized gradient approximation of density functional theory is applied to study the hydrogen storage capacity of the alkali metal atom Li, transition metal atoms Ti and Fe decorated C₁₈B₂M(M=Li, Ti, Fe) fullerefles. It is found that the metal is bonding to C₁₈B₂ stronger than to C₂₀. When the average adsorption energy of C₁₈B₂Li-nH₂ is low, and the binding of H₂ to C₁₈B₂Fe is too strong, C₁₈B₂Ti-nH₂ has the average adsorption energy between 0.45-0.59 eV, which is in the range from 0.2 to 0.6 eV, so it can realize the reflersible adsorption of H₂. A maximum number of H₂ adsorbed on to C₂₀B₂M(M=Li, Ti, Fe) should be 4, 6, and 4, for Li, Ti, and Fe respectively; this agrees well with the 18 electronic rule. C₁₈B₂Li adsorbs H₂ molecules mainly through the static electronic field formed by Li ions, while C₁₈B₂Ti and C₁₈B₂Fe adsorb H₂ mainly through the Kubas interaction. Therefore, C₁₈B₂Ti can not only adsorb more H₂ molecules, but also realize the reflersible hydrogen storage.