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利用第一性原理方法研究了掺杂元素Ti,Ni对NaAlH4放氢性能的影响.计算表明:Ti在NaAlH4中倾向于替代Al原子,而Ni则倾向于占据间隙位置.电子结构分析显示Ti替代NaAlH4中的Al位置时与近邻的Al原子产生强烈的相互作用,破坏[AlH4]基团的结构,从而改善NaAlH4的放氢性能.Ti替代Na或占据间隙位置时Ti与H原子间存在较强的相互作用,有可能诱发TiH2相而改善NaAlH4的放氢性能.与Ti相比Ni对NaAlH4放氢性能的影响较小,仅当Ni占据间隙位置时才可能对[AlH4]基团产生一定影响.总体而言,Ti对NaAlH4放氢性能的影响强于Ni的作用,这与实验观测相吻合.
The influence of doping elements Ti and Ni on the dehydrohalogenation properties of NaAlH4 was studied by the first-principles method. The calculations show that Ti tends to replace Al atoms in NaAlH4 and Ni tends to occupy interstitial sites. The electronic structure analysis shows that Ti substitution The Al site in NaAlH4 strongly interacts with the neighboring Al atoms, destroying the structure of [AlH4] groups and thus improving the hydrogen desorption performance of NaAlH4. When Ti substitutes for Na or occupies the interstitial sites, there is a strong interaction between Ti and H atoms , It is possible to induce the TiH2 phase to improve the hydrogen desorption performance of NaAlH4. Compared with Ti, the effect of Ni on the desorption performance of NaAlH4 is small. It is only possible to influence the [AlH4] group when Ni occupies the interstitial position In general, the effect of Ti on the dehydrohalogenation of NaAlH4 is stronger than that of Ni, which agrees well with the experimental observations.