Calcium-decorated boron-carbide T-graphene nanocage for hydrogen storage: A DFT study

The Boron-carbide T-graphene (BC) nanocage, functionalized with a calcium (Ca) atom as an alkaline-earth metal dopant, was investigated for its potential as a high-capacity hydrogen storage material. All calculations were performed using density functional theory (DFT) at the B3LYP/6-311G(d,p) level of theory. A single Ca atom was initially decorated into the BC nanocage to evaluate its hydrogen adsorption capabilities. The results of Natural Bond Orbital (NBO) Analysis, molecular electrostatic potential (MEP) maps, and quantum theory of atoms in molecules (QTAIM) analysis revealed that the incorporation of Ca atoms with BC (Ca–BC) enhanced the adsorption of H₂ molecules. The Ca–BC nanocage demonstrated the ability to adsorb up to six H₂ molecules per Ca atom, with an average adsorption energy of approximately −0.20 eV per H₂ molecule, indicating physisorption. To further assess the hydrogen storage capacity, the BC nanocage was doped with the maximum possible number of Ca atoms (six Ca atoms, denoted as 6Ca–BC). This system exhibited a high gravimetric hydrogen storage capacity of 8.7 wt%, highlighting the potential of the Ca–BC nanocage as an excellent candidate for H₂ storage applications.