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基于密度泛函理论的第一性原理,研究了掺杂元素Ti,Nb和Zr取代Ca原子后对Ca(BH4)2·2NH3储氢性能的影响.通过计算体系的晶体结构、占位能、态密度及电子密度拓扑性质,分析了原子间的成键情况和结构稳定性.结果表明:Ti,Nb,Zr分别取代Ca(BH4)2·2NH3中的Ca原子,Ti取代最容易形成稳定结构,Zr次之,Nb最难形成.Ca(BH4)2·2NH3结构中,B—H,N—H键都以共价作用为主,且N—H键比B—H键作用强.掺杂原子取代后改变BH4基团的稳定性,同时掺杂原子对N作用增强,减弱NH3分子释放对脱氢的影响.Nb原子取代对B—H影响最大,最能改善Ca(BH4)2·2NH3体系的脱氢性能,使H更易脱去.
Based on the first principle of density functional theory (DFT), the effects of substitution of Ti, Nb and Zr for Ca atoms on the hydrogen storage capacity of Ca (BH4) 2.2NH3 were studied. By calculating the crystal structure, State density and electron density, the bonding state and the structural stability between atoms were analyzed. The results show that Ti, Nb and Zr replace the Ca atoms in Ca (BH4) 2 · 2NH3, respectively, and the substitution of Ti is most likely to form a stable structure , Zr is the second, Nb is the most difficult to form.Ca (BH4) 2 · 2NH3 structure, B-H, N-H bond covalently dominated, and N-H bond stronger than B-H bond. The substitution of heteroatoms can change the stability of BH4 group, meanwhile, the doping effect of N atom on N is weakened and the effect of NH3 molecule release on dehydrogenation is weakened.Nb atom substitution has the strongest influence on B-H, which can improve Ca (BH4) 2 · The dehydrogenation performance of 2NH3 system makes H easier to remove.