Ti对LiAlH_4储氢性能的影响

The effects of titanium on hydrogen storage properties of LiAlH_4

为了降低LiAlH4的吸放氢温度及提高其吸放氢速度,采用基于密度泛函理论(DFT)的平面波赝势(PW-PP)方法,计算了Ti掺杂在LiAlH4中取代不同位置的Li、Al前后的电子结构及相关热力学性质。结构优化之后,热力学稳定性较好的构型有4种:Li3Al4H16Ti、Li4Al3H16Ti、Li3Al4H17Ti、Li4Al3H17Ti,其对应的缺陷形成能分别为1.31、0.60、1.21、1.27 eV。掺杂前后LiAlH4的电子态密度并无明显变化。在LiAlH4化学势变化曲线图中,TiAl3的化学势变化曲线与反应物LiAlH4、Li3AlH6等的并没有相交。上述结果表明,单质的Ti对LiAlH4的分解并没有起到实质的催化作用。

In order to reduce the hydrogen absorption and desorption temperature of LiAlH4 and to improve the rate of hydrogen absorption and desorption,situations of Ti point defects in LiAlH4 were studied with the plane-wave pseudo-potential（PW-PP） method based on the density functional theory（DFT）.Four types of models having better thermodynamic stability could be formulated with Li3Al4H16Ti,Li4Al3H16Ti,Li3Al4H17Ti and Li4Al3H17Ti relatively.The Ti defect formation energies are 1.31eV,0.60 eV,1.21 eV and 1.27eV respectively.The electronic density of state（DOS） do not change obviously compare to that of pure LiAlH4 crystal.The curves of TiAl3 and reactants do not intersect in the chemical potentials change graphical of LiAlH4.These results show that simple substance Ti does not play a substantial role in the hydrogen storage properties of LiAlH4.