DFT calculations on the catalytic oxidation of CO over Si-doped (6,0) boron nitride nanotubes

The oxidation of carbon monoxide (CO) is important for a series of technological and environmental applications. In this work, the catalytic oxidation of CO on Si-doped (6,0) boron nitride nanotubes (BNNTs) is investigated by using density functional theory calculations. Reaction barriers and corresponding thermodynamic parameters were calculated using the M06-2X, B3LYP and wB97XD density functionals with 6-31G* basis set. Our results indicate that a vacancy defect in BNNT strongly stabilizes the Si adatom and makes it more positively charged. This charging enhances the adsorption of reaction gases (O-2 and CO) and results in the change of the electronic structure properties of the tube. The calculated barrier of the reaction CO + O-2 -> CO2 + O-ads on Si-doped BNNTs following the Langmuir-Hinshelwood is lower than that on the traditional noble metal catalysts. The second step of the oxidation would be the Eley-Rideal reaction (CO + O-ads -> CO2) with an energy barrier of about 1.8 and 10.1 kcal/mol at M06-2X/6-31G* level. This suggests that the CO oxidation catalyzed by the Si-doped BNNTs is likely to occur at the room temperature. The results also demonstrate that the activation energies and thermodynamic quantities calculated by M06-2X, B3LYP and wB97XD functionals are consistent with each other.