Hydrogen adsorption on Pt-decorated closed-end armchair (3,3), (4,4) and (5,5) single-walled carbon nanotubes

Structures of small lengths of capped (3,3), (4,4) and (5,5) single-walled carbon nanotubes (SWCNTs) and their structures decorated by Pt atom and Ptn clusters (n = 2–4) were obtained using density functional theory calculations. Binding abilities of Pt atom and Ptn clusters on the outer surface of SWCNTs at various adsorption sites were explored. Adsorptions of H2 onto Pt atom of the Pt-decorated (3,3), (4,4) and (5,5) SWCNTs were studied and their adsorption energies are reported. The thermodynamic properties and equilibrium constants for H2 adsorptions on the Pt4-decorated (3,3), (4,4) and (5,5) SWCNTs were obtained. The adsorption of H2 on the Pt atom of the Pt4/(3,3) SWCNT was found to be the most preferred reaction of which enthalpy and free energy changes at room temperature are −46.61 and −23.99 kcal/mol, respectively.