Adsorption of small gases on carbon nanotube-supported metal clusters

Abstract

The structures of various lengths of closed-end armchair (3,3), (4,4) and (5,5) single- walled carbon nanotubes (SWCNTs) and their platinurm-clusters (Ptn,n=1 to 4 atom) decorated structures were obtained using DFT/B3LYP calculations. Binding abilities of Pt cluster on SWCNTs at various carbon adsorption sites were investigated. Hydrofen adsorption onto platinum atom of Pt4-decorated (3,3), (4,4) and (5,5) SWCNTs were studied and their adsorption energies are reported The thermodynamic properties and equilibrium properties and equilibrium constants for hydrogen adsorption on Pt4-decorated (3,3), (4,4) and (5,5) SWCNTs are reported. The hydrogen adsorption on platinum atom of the Pt4/(3,3) SWCNT was found to be the most preferred process of which enthalpy and free energy changes are -46.61 and -23.99 kcal/mol, respectively. The adsorption energy of CO, O2, N2, CO2, N2O, NO2, SO2< H2O and NH3 on platinum atom of the Pt4-decorated (3,3), (4,4) and (5,5) SWCNTs were obtained. The hydrogen adsorption abilities on platinum group metals Clusters are in same order on (3,3), (4,4) SWCNTs : Os4> Ir4> Pd4> Ru4> Rh4 that are different from the hydrogen adsorptions on (5,5) SWCNT of which order : Os4> Ir4> Rh4> Pd4> Ru4/ SWCNTs.