采用基于密度泛函理论（DFT）的第一原理方法,研究了外加电场对单层AlN薄片储氢性能的影响。通过几何优化得到AlN薄片最稳定的吸氢位置为N原子顶位。研究结果表明：在一定范围内,随着外加电场强度的增加,H2分子在AlN薄片上的吸附能逐渐增大,N—H键长越来越小,H—H键长越来越大。态密度分析表明,加上外电场之后,H-1s轨道与N-2p轨道杂化导致N与H间的交互作用增强。说明电场极化使AlN薄片与H2分子结合得更加紧密,大大提高了AlN薄片的储氢稳定性。而一旦撤销外加电场,H2分子又能恢复到在AlN薄片上的物理吸附状态,使得吸放氢可逆。研究还发现在电场作用下,可同时在AlN薄片的上下表面各吸附一层H2分子,储氢容量显著提高。
Hydrogen storage properties of single AlN sheet under an applied electric field was investigated by using the first-principles method based on the density functional theory.It is found that the relaxed structure of a H2 molecule adsorbing on the AlN sheet is the most stable one compared with other relaxed structures.Our investigations reveal that the adsorption energy of a H2 molecule on the AlN sheet become larger with increasing electric field in a certain range.Density of states（DOS） shows the hybridization of H-1s with N-2p results in the increased interaction between the N and H atom in the presence of the electric field.Applied electric field can enhance the interaction between the AlN sheet and the H2 molecule and improve the hydrogen storage properties of the AlN sheet.Once the applied electric field is removed,the H2 molecule can preserve its original physical adsorption state on the AlN sheet.A reversible hydrogen adsorption and desorption cycle is thus obtained by applying or removing an electric field.Hydrogen storage capacity will be increased drastically when two layers of H2 is adsorbed on both side of the AlN sheet in the presence of a suitable electric field.
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