Surface adsorption and encapsulated storage of H2 molecules in a cagelike (MgO)12 cluster

Abstract

Cluster-based materials are candidate materials for solid-state hydrogen storage owing to their special geometric and electronic structures. The surface adsorption and the encapsulated storage of H2 molecules in a cagelike (MgO)12 cluster have been studied using density functional theory (DFT) calculations including a dispersion interaction. 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%. Compared with dispersion-corrected DFT calculations, the traditional DFT method substantially underestimates the surface adsorption strength. According to symmetric configurations, a maximum capacity of six H2 molecules can be stored in the interior space of the cagelike (MgO)12 cluster. The encapsulated H2 molecules are trapped by stepwise energy barriers of 0.433–2.550 eV, although the storage is an endothermic process. The present study will be beneficial for hydrogen storage in cagelike clusters and assembled porous materials.