Endohedral doping of Ca12O12-X (X = Zn, Cd, and Hg) as hydrogen storage materials

Abstract

The emergence of hydrogen storage materials has drawn a lot of insurmountable attention in the scientific community due to the burgeoning demand for energy. As hydrogen not only performs well in various processes but can also be used as a source of alternative energy when paired with a cell technology like a fuel cell, it has gained increased significance. Herein, efforts are being undertaken to create effective hydrogen storage materials based on Ca12O12 nanocages that have been endohedrally encapsulated with transition metals (TMs) (zinc, cadmium, and mercury). The synthesis of endohedrally doped Ca12O12 is a complex process that involves solid-state reaction and diffusion of the modelled dopant atoms (zinc, cadmium, and mercury) into the internal cage. Thus, DFT calculations herein provide valuable insights into the underlying mechanisms and properties of the resulting doped materials. For all the systems under study, quantum chemical calculations were carried out using density functional theory (DFT) and time-dependent DFT at the PBE0/def2SVP level of theory. The adsorption energies of 10H2@ Ca12O12, 10H2@ZndopCa12O12, 10H2@CddopCa12O12, and 10H2@HgdopCa12O12 systems were obtained in the range of −34.47 to 130.86 kcal/mol respectively and portrayed the efficient adsorption of H2 on the metal-encapsulated systems. Also, considerable stabilization of the systems was obtained with higher charge separation which evidently correlates with the adsorption energy parametric values. Strong hydrogen bond and van der waals interaction was observed as the dominant interactions with a considerable binding energy of −9.72 kcal/mol. The proposed designed H2-adsorbed metal-encapsulated Ca12O12 systems are effective systems for designing time-ahead hydrogen storage materials, according to the results of all investigations and global descriptions of reactivity.