Silicon-, Nitrogen-Doped Single-Walled Carbon Nanotubes as Oxygen Reduction Reaction Catalysts

Single-walled carbon nanotubes doped with silicon and nitrogen atoms, SiС 138 N 4 and SiC 137 N 6 , were studied at the DFT ωB97XD/DGDZVP level. Analysis of the atomic charges allowed determination of the most probable sites of oxygen adsorption, namely, the silicon atom in the N x ( x = 3 and 4) environment and the C=C bond near the SiN x fragment. The free energy profiles of the oxygen electroreduction reaction in acidic and alkaline media on the active sites of model catalysts were obtained. It was found that the silicon-, nitrogen-doped carbon nanotubes with the silicon atom in the center of a planar SiN 4 fragment can show superior catalytic properties due to the activation of the carbon atoms adjacent to this fragment.