Hydrogen adsorption on Ge52−, Ge92− and Sn92− Zintl clusters: A DFT study

Abstract

Hydrogen storage is a subject of extensive research because hydrogen is a clean and eco-friendly for future applications. New strategies are being developed simultaneously for the easy and effective storage of hydrogen gas. Herein, we report the hydrogen adsorption on the Germanium and Silicon Zintl clusters within the framework of density functional theory (DFT). The excellent adsorption of hydrogen on Ge52−, Ge92−, Si92− based Zintl clusters is achieved in terms of adsorption energies, electronic properties such as, HOMO-LUMO gaps, natural bond orbital (NBO) charge transfer, variation in dipole moment and density of state analysis (DOS). The superior adsorption affinities of these Zintl clusters are demonstrated in comparison with the adsorption capability of Ge and Si neutral clusters. In comparison, the adsorption energies of H2@Zintl phase complexes are higher than those of corresponding H2@neutral clusters. For example, the adsorption energy of b-exo-H2@Si92− complexes is −11.13 kJ mol−1 which is far higher than −3.47 kJ mol−1 for the neutral analogue (b-exo-H2@Si90). The effect of hydrogen adsorption on the EH-L gaps in Zintl clusters is also more pronounced, and the higher charge transfer is observed as well. Overall, results suggest the higher adsorption strength of Zintl cluster for H2 as compared to neutral clusters.