Surface Adsorption and Encapsulated Storage of H₂ Molecules in a Cagelike (MgO)₁₂ Cluster

The cluster with a cagelike structure could enable the storage of H₂ molecules via surface adsorption and encapsulated storage. Surface adsorption involves the interaction between H₂ and host clusters. Encapsulated storage involves the storage of H₂ in the interior space of the cagelike structure. The latter is essential for practical applications of cagelike clusters because the interior space is retained when they are assembled into solid-state materials, although many surface adsorption sites are occupied. Here, we report an investigation on surface adsorption and encapsulated storage of H₂ molecules in the cagelike (MgO)₁₂ cluster based on a dispersion-corrected density functional theory calculation. The results revealed that the cagelike (MgO)₁₂ cluster surface can adsorb 24 H₂ molecules with an average adsorption energy of 0.116 eV/H₂, which brings about a gravimetric density of 9.1 wt%. Inside the cagelike (MgO)₁₂ cluster, a maximum capacity of six H₂ molecules could be stored according to symmetric configurations. The encapsulated H₂ molecules are trapped by energy barriers no more than 2.55 eV, although the storage is an endothermic process.