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

<p>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 Pt<i><sub>n</sub></i> clusters (<i>n</i> = 2–4) were obtained using density functional theory calculations. Binding abilities of Pt atom and Pt<i><sub>n</sub></i> clusters on the outer surface of SWCNTs at various adsorption sites were explored. Adsorptions of H<sub>2</sub> 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 H<sub>2</sub> adsorptions on the Pt<sub>4</sub>-decorated (3,3), (4,4) and (5,5) SWCNTs were obtained. The adsorption of H<sub>2</sub> on the Pt atom of the Pt<sub>4</sub>/(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.</p>