Catalytic activity of silicon carbide nanotubes and nanosheets for oxidation of CO: a DFT study

As is well-known, searching for an efficient catalyst that can oxidize CO molecules is of great importance in the removal of this poisonous gas. Using density functional theory calculations, we report the oxidation of CO by molecular O-2 on a finite-sized silicon carbide nanotube (SiCNT) and nanosheet (SiCNS). Both Eley-Rideal (ER) and Langmuir-Hinshelwood (LH) oxidation mechanisms are considered. The CO oxidation by O-2 on SiCNT and SiCNS surfaces occurs via a two-step mechanism: (1) O-2 + CO -> OOCO -> O-ads + CO2 and (2) O-ads + CO -> OCO -> CO2, proceeding via LH and ER mechanisms, respectively. The activation energies of these two steps over the SiCNT (SiCNS) are 0.86 (0.27) and 0.97 (0.12) eV, respectively. Results indicate that the CO oxidation over the SiCNS is more favorable than that over the SiCNT, due to its lower energy barriers. In addition, the increasing of the tube length and curvature effects on the adsorption of an O-2/CO molecule is also studied. This study has useful guidance for fabricating SiCNTs and SiCNSs for CO oxidation with high activity properties.