Surface oxygen species essential for the catalytic activity of Ce-M-Sn (M = Mn or Fe) in soot oxidation

Herein, transition metal (Mn and Fe)-doped Ce-Sn nanorod catalysts were successfully synthesized via a hydrothermal method. The obtained catalysts were evaluated for soot oxidation activity by temperature programmed oxidation reaction tests under loose contact. It was clearly found that the Mn-doped Ce-Sn catalyst exhibited the highest catalytic activity, with Delta T-10, Delta T-50 and Delta T-90 values of 56 degrees C, 56.2 degrees C and 45.4 degrees C, lower than those of the Ce0.5Sn0.5O2 catalyst. The Ce0.5Mn0.2Sn0.3O2 catalyst also possessed outstanding and stable resistance to H2O. Finally, all the prepared catalysts were characterized by XRD, TEM, SEM, BET, H-2-TPR, XPS, and Raman spectroscopy. The results suggested that doping with Mn or Fe was beneficial to the generation of more Ce3+, which was linked to surface oxygen vacancies. Surface oxygen vacancies were beneficial to accelerating the formation of surface-active oxygen species. Interestingly, a linear relationship existed between the Ce3+/Ce4+ ratio and the density of surface-active oxygen species. It was also found that there was a linear relationship between the amount of surface-active oxygen and the utilization efficiency of NO2, which could diffuse into soot in the gas phase to improve soot oxidation. In short, this study demonstrates that surface-active oxygen is crucially important in NO2-assisted soot oxidation.

Automated summary

Transition metal-doped Ce-Sn nanorod catalysts were synthesized successfully and Mn-doped catalyst showed the highest catalytic activity. The surface-active oxygen was crucial in NO2-assisted soot oxidation.