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

The adsorption/dissociation of the O-2 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 O-2. Unlike the case for carbon nanotubes, the chemisorption of triplet O-2 oil SiCNTs is exothermic with remarkable charge transfer from nanotubes to the O-2 molecule. Singlet O-2 adsorption oil the Surface of SiCNTs can yield cycloaddition structures with large binding energies and sizable charge transfer. The reaction mechanism studies show that for triplet O-2, the chemisorption configuration is favorable, but the cycloaddition configuration is preferred for singlet O-2. For singlet O-2, we also Studied the dissociation of the O-2 molecule, and a two-step mechanism was presented. The dissociation of molecular O-2 results in formation of two three-membered rings with large binding energies. The key to the dissociation process of singlet O-2 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 O-2 are shown to be dramatically influenced.