Unveiling the mechanism of CO–SCR reaction over Ir/SiO2 catalyst in the presence of multiple components (CO, O2, SO2)

Controlling both CO and NOx pollutants without additional cost is necessary but challenging, especially in industrial flue gas with complex components. Previous studies mainly focused on the effect of O 2 and SO 2 on the CO oxidation side reaction and valence state of Ir species on various catalysts, while neglecting the impact on NO conversion pathway. Herein, we propose an "ineffective reaction pathway" in the presence of O 2 with nitrate as an intermediate according to the results of in situ DRIFTS and DFT. And we also reveal the contribution of SO 2 in inhibiting the adsorption of O 2 and promoting the selective adsorption of NO and CO even at lower injection concentrations, based on the oxidation of SO 2 on Ir(111). This is quite a favorable characteristic for the treatment of industrial flue gas, resolving the long–standing dispute on the involvement of these components in the CO–SCR reaction. Under specific conditions (CO/NO=20, O 2 =5%, SO 2 =200 ppm) at 250 °C, the NOx conversion is as high as 78%. These results will contribute to the development of more efficient catalysts in the future for simultaneously controlling two pollutants (CO and NOx).