Theoretical Study of O2 Molecular Adsorption and Dissociation on Silicon Carbide Nanotubes

Abstract

The adsorption/dissociation of the O2 molecule on the surface of silicon carbide nanotubes (SiCNTs) was investigated by density functional theory. We found several adsorption configurations, including chemisorption and cycloaddition configurations, for triplet and singlet O2. Unlike the case for carbon nanotubes, the chemisorption of triplet O2 on SiCNTs is exothermic with remarkable charge transfer from nanotubes to the O2 molecule. Singlet O2 adsorption on the surface of SiCNTs can yield cycloaddition structures with large binding energies and sizable charge transfer. The reaction mechanism studies show that for triplet O2, the chemisorption configuration is favorable, but the cycloaddition configuration is preferred for singlet O2. For singlet O2, we also studied the dissociation of the O2 molecule, and a two-step mechanism was presented. The dissociation of molecular O2 results in formation of two three-membered rings with large binding energies. The key to the dissociation process of singlet O2 on the SiCNT surface is the first step with a barrier energy of 0.40 eV. Finally, the electronic properties of SiCNTs with adsorbed triplet and singlet O2 are shown to be dramatically influenced.