Density functional study of physisorption of H molecules on scandium and yttrium decorated C fullerene: prospect for hydrogen storage.

CONTEXT

Hydrogen storage in porous nanostructured compounds have recently attracted a lot of attention due to the fact that the underlying adsorption mechanism and thermodynamics provide suitable platform for room temperature adsorption and desorption of H molecules. This work reports the findings of a study on the reversible hydrogen storage capacities of Sc and Y decorated C fullerene, conducted using dispersion-corrected density functional theory (DFT) calculation. The transition metal (TM) atoms, such as Sc and Y, are identified to attach to the C-C bridge position of the C fullerene through non-covalent closed-shell interactions. This suggests that the interaction between the TM atoms and the fullerene occurs via weak van der Waals forces rather than stronger covalent bonds. The thermodynamic stability of the decorated fullerene structures is assessed using different reactivity descriptors. Each Sc and Y atom attached to the C fullerene is capable of absorbing maximum of 6 and 7 numbers of hydrogen molecules, respectively. This results in practical gravimetric densities of up to 4.0 wt% and 4.04 wt% at a temperature of 300 K and a pressure of 60 bar. These findings highlight the significant hydrogen storage capacities of the decorated fullerene structures, indicating their potential for practical use in hydrogen storage systems. The average adsorption energy of H molecules is found lying in the range of 0.332-0.276 eV implying the adsorption process to be physisorptive. Overall, the study provides valuable insights into the hydrogen storage capabilities of Sc and Y decorated C fullerene complexes, offering a promising avenue for the development of efficient and reversible hydrogen storage materials for clean energy applications.

METHODS

Geometry optimization and other electronic structure calculations was performed by Gaussian 09 software using density functional theory (DFT) with the B3LYP-D3 and M06-2X functionals and the basis set 6-311 + G(d,p). The dispersion-corrected and hybrid meta-exchange correlation functionals were employed because of their accuracy in describing non-covalent interactions, rendering them appropriate for investigating hydrogen adsorption on surfaces.