外电场对锂修饰氧化石墨烯结构储氢性能的影响

Effects of External Electric Field on Hydrogen Storage Performance of Li-decorated Graphene Oxide

基于密度泛函理论(DFT)的第一性原理方法,研究了外加电场对锂修饰氧化石墨烯结构(Li@GO)储氢性能的影响.考察Li@GO结构的稳定性及其对外加电场的响应,研究H_2-Li@GO结构的H_2分子吸附能、几何构型与外加电场的关系.研究结果表明,当外加电场方向垂直Li@GO平面向下(负电场)时,随电场强度增加,H_2分子的吸附能逐渐降低,H_2分子逐渐接近Li原子;当外加电场方向向上(正电场)时,随电场强度增加,H_2分子的吸附能逐渐升高,H_2分子逐渐远离Li原子,分波态密度(PDOS)分析表明:与无外加电场体系的PDOS相比,当对体系施加负电场时,H_2-Li的杂化峰向低能量方向位移,H_2分子与Li@GO结合更加紧密,提升了储氢稳定性;施加正电场时,H_2-Li的杂化峰向高能量方向位移,H_2分子与Li@GO作用减弱提升了氢气释放动力学性能.进一步计算表明,在无外加电场情况下,Li@GO结构最大储氢量在3.1%以上.

Hydrogen storage performance of Li decorated graphene oxide（GO） under an external electric field was investigated with the first-principle method based on the density functional theory（DFT） calculations.Firstly the stability of Li@ GO structure due to the adsorption of Li atoms at different binding sites on GO structure was investigated.Then a stable Li@ GO structure was obtained and dependences of the structural stability and H2 adsorption of the Li@ GO structure on the electric field were discussed.The results indicate that both the H2 adsorption energy,E（ad）,and the distance between H2 and Li atom,d（Li-H2）,decrease with the increasing intensity of the downward electric field.While both E（ad） and d（Li-H2） increase with the increasing intensity of the upward electric field.From the partial density of state（PDOS） analysis,the H2-Li hybridization peaks under a negative electric field shifted to the larger negative energy region compared to those without an electric field,which indicates the H2-Li@ GO system becomes more stable under the negative electric field.When the positive electric field was added,the H2-Li hybridization peaks shifted to the smaller negative energy region,which indicates the interaction between H2 and Li becomes weaker.It is therefore anticipated that the adsorption-desorption processes of H2 on Li@ GO structure can be easily controlled by adding an electric field with appropriate intensity and direction.Further calculation indicates the Li@ GO structure has a maximum hydrogen storage capability of larger than 3.1%without the external electric field.