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

Abstract— Single-walled carbon nanotubes doped with silicon and nitrogen atoms, SiС₁₃₈N₄ and SiC₁₃₇N₆, 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 SiN₄ fragment can show superior catalytic properties due to the activation of the carbon atoms adjacent to this fragment.