A DFT comparative study of single and double SO₂ adsorption on Pt-doped and Au-doped single-walled carbon nanotube

Highlights: • Investigation of the adsorption of SO₂ on Au/SWCNT and Pt/SWCNT. • SO₂ adsorbed on Au/SWCNT and Pt/SWCNT system demonstrate a strong chemisorption. • NBO analysis was done to reach more understanding about intermolecular interactions. - Abstract: Adsorption of single and double SO₂ gas molecule(s) on the surface of Pt-doped and Au-doped (5,5) single-walled carbon nanotubes (Pt/CNT-V and Au/CNT-V) were investigated by using density functional theory (DFT) at B3LYP/LANL2DZ level. The results showed the following: firstly, adsorption on Au/CNT-V is independent of special orientation, secondly, SO₂ adsorption on Pt/CNT-V in single case is stronger than Au/CNT-V, and finally, adsorption of the first molecule influences adsorption of the second one. Upon adsorption of SO₂ molecule(s), the energy gap of Pt/CNT-V were considerably reduced, resulting in enhanced electrical conductivity but in Au/CNT-V, despite of adsorption energy similar to Pt/CNT-V, E_g slightly increased. In order to consider the effect of adsorption on electronic properties, DOS and PDOS calculations were performed. Moreover, NBO analysis was done to reach more understanding about intermolecular interactions. In conclusion, chemical reactivity was investigated in terms of chemical hardness, softness and work function (ϕ)