Theoretical Study of Hydrogen Storage in lower diamondoids: adamantane and diamantane

In recent years, much effort has been dedicated to fabricate carbon based nanostructures, which can absorb hydrogen molecules with high storage capacity. Different nanostructured materials have been studied in detail to enhance hydrogen storage capacity such as powdered graphite, carbon nanotubes and graphene. Several studies on graphene have highlighted the potential application of this unique material for hydrogen storage as a promising media for the efficient solid-state hydrogen storage systems [1, 2]. But according to our knowledge, there is no work and research of the ability to absorb the hydrogen gas by adamantane and diamantane (lower diamondoids), which are found major applications as templates and as molecular building blocks in nanotechnology and host-guest [3,4]. In this paper, we have investigated the ability to absorb hydrogen by adsorption on the outer and inner sites of adamantane and diamantane with applying ab initio-DFT calculations. The results show that hydrogen molecule is well absorbed by both ways, and adamantan shows a high potential for absorption of hydrogen molecules. Although the free energy of the Gibbs of adsorption, when the hydrogen molecule is encapsulated inside adamantane cage, is more negative, indicating that adsorption is better than inner sites.