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

Single-walled carbon nanotubes doped with silicon and nitrogen atoms, SiC138N4 and SiC137N6, were studied at the DFT omega B97XD/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 SiNx 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.