Mechanistic Insights into the Influence of Preparation Methods and Fe3+ Doping on the Low-Temperature Performance of Mnceox Catalyst for Nh3-Scr Reaction

Aiming to polish up the denitrification efficiency and N2 selectivity for MnCeOx catalyst at low temperature, an array of Fe3+-doped MnCeOx catalysts were synthesized through innovative approaches: the citric acid method (FeMnCeOx-CA) and CTAB-assisted template method (FeMnCeOx-ST). However, the CTAB-assisted template method did not exhibit a positive impact on enhancing the low temperature activity of MnCeOx and FeMnCeOx catalysts. Conversely, the citric acid method demonstrated a significant enhancement to remove NOx of MnCeOx and FeMnCeOx catalysts below 300 °C. Therefore, an in-depth investigation of underlying impact of citric acid method and Fe3+ doping on MnCeOx catalyst was thoroughly implemented. The NH3-SCR performance of FeMnCeOx-CA exceed 90% NOx conversion within 75-150 °C, and it can be reached 94% NOx conversion at 125 °C, which was almost 10% higher than that of MnCeOx-CA catalyst. Moreover, the N2O formation of FeMnCeOx-CA is significantly suppressed at temperatures ranging from 125-200 °C, exhibiting a higher N2 selectivity compared to MnCeOx-CA. Besides, solid solution structure of -Ce-O-Mn-O-Fe- strengthened surface acidity and redox ability over FeMnCeOx-CA catalyst, promoting NH3 adsorption and activation. On the other hand, the electronic interaction among the active components was also facilitated, which ultimately expedited the redox cycle and further obtaining favorable low temperature catalytic activity. Finally, a reasonable Langmuir-Hinshlwood mechanism and detailed reaction pathways of NH3-SCR reaction existed on FeMnCeOx-CA catalyst were also proposed.