Calcium-decorated carbyne networks as hydrogen storage media

摘要

Among the carbon allotropes, carbyne chains appear outstandingly accessible for sorption and very light. Hydrogen adsorption on calcium-decorated carbyne chain was studied using ab initio density functional calculations. The estimation of surface area of carbyne gives the value four times larger than that of graphene, which makes carbyne attractive as a storage scaffold medium. Furthermore, calculations show that a Ca-decorated carbyne can adsorb up to 6 H_2 molecules per Ca atom with a binding energy of ～0.2 eV, desirable for reversible storage, and the hydrogen storage capacity can exceed ～8 wt %. Unlike recently reported transition metal-decorated carbon nanostructures, which suffer from the metal clustering diminishing the storage capacity, the clustering of Ca atoms on carbyne is energetically unfavorable. Thermodynamics of adsorption of H_2 molecules on the Ca atom was also investigated using equilibrium grand partition function.