Si-embedded boron-nitride nanotubes as an efficient and metal-free catalyst for NO oxidation

We study the catalytic capability of Si-embedded boron nitride nanotubes (Si-BNNTs) as a metal-free catalyst for NO oxidation by using density functional theory. Our results reveal that a vacancy defect in BNNT strongly stabilizes the Si adatom and makes it more positively charged. These results confirm the fact that Si-BNNTs are stable enough to be utilized in catalytic NO oxidation reactions. The complete NO oxidation reactions involve the direct oxidization of NO to NO2 by O2 adsorbed on the surface of Si-BNNTs, as in NO + O2 → NO2 + O. The remaining O atom can further oxidize NO to NO2. The calculated energy barriers range from 0.2 to 2.4 kcal/mol, which suggests that the NO oxidation catalyzed by the Si-BNNTs is likely to occur at the room temperature. These values are much less than those processes using noble metal catalysts.