Density functional theory calculations are performed to investigate the mechanisms of N2O reduction by SO2 over Si- and C-doped (6,0) boron nitride nanotubes (BNNTs). According to our results, the Si or C adatom can be strongly stabilized over the vacancy defect of the BNNT. The adsorption energy of Si and C atoms over defective BNNT is calculated to be -297.3 and -333.7 kcal/mol, respectively, indicating a strong interaction between these dopant atoms and the tube surface. The N2O reduction reaction includes the decomposition of N2O (i.e. N2O → N2 + O*), followed by the reduction of O* by SO2 molecule (i.e. SO2 + O* → SO3). The calculated energy barrier of the SO2 + O* → SO3 reaction on Si- and C-doped BNNTs is 2.4 and 5.4 kcal/mol, respectively. Moreover, the effects of tube diameter and length on the N2O reduction are studied in detail. The disproportionation of N2O molecules (2N2O → 2N2 + O2) over both surfaces needs a quite large activation energy, which indicates the impossibility of this reaction at ambient condition. The results show that both Si- and C-doped BNNTs can be viewed as an effective green catalyst for the reduction of N2O.
