Hydrogen storage capacity of C12X12 (X = N, P, and Si)

• Carbon base materials: C 12 N 12 , C 12 P 12 and C 12 Si 12 were investigated using DFT as storage materials for hydrogen molecule. • adsorption is thermodynamically favored with negative values for Gibbs free energy and change in Enthalpy. • The weak interactions obtained for examined adsorptions suggest and excellent hydrogen molecule trapping • The decrease in HOMO-LUMO gap and the plot for DOS confirms the adsorption properties. • C 12 P 12 nanocage provides the optimum surface for adsorbing the hydrogen molecule. • The result obtained for adsorption energies is consistent with that for ELF. Nanomaterials have attracted great interest in recent years due to their unique surface properties. The high surface to volume ratio of these materials has significant implications with respect to energy storage. Hydrogen adsorption on modified nanocages: C 12 N 12 , C 12 P 12 and C 12 Si 12 are investigated by density functional theory (DFT) calculations at the ωB97X-D/6-311+G (d,p) level of theory. The findings of the surface analysis and the examination of the natural bond orbitals showed that charge transfer occurred throughout the adsorption process. From the ELF analysis, the electron shared between C 12 P 12 and C 12 Si 12 and the chemical bond formed with the hydrogen molecule infers chemisorption which is consistent with the adsorption energy. C 12 N 12 showed molecular physisorption with an E ads of -0.99 eV, whereas C 12 P 12 and C 12 Si 12 showed chemisorption behavior, the molecular adsorption energy of -2.50 eV was obtained for C 12 P 12 and is observed to be the highest. Therefore, in contrast to other materials, C 12 P 12 is ideal for the storage and adsorption of hydrogen molecules. The negative value for Eads depicts that adsorption of the said molecule is thermodynamically favorable. Furthermore, from the analysis of the NCI the nature of interaction is associated to Vdw and confirms excellent interaction between hydrogen molecule and the adsorbent surfaces.