Comparison of Mn doped CeO2 with different exposed facets for NH3-SCR at low temperature

Herein, the Mn-doped different exposed crystal surfaces of CeO 2 were prepared and used for the low-temperature NH 3 -SCR process. The results showed that Mn/CeO 2 -NC catalyst possessed the higher catalytic activity than Mn/CeO 2 -NP and Mn/CeO 2 -NR catalysts at low temperature, which achieved over 90% NO conversion at 200 °C. XRD and SEM analysis verified that though the grain size was different, the active manganese species still maintained the highly uniform distribution on all catalysts. The excellent low-temperature redox property and strong surface acidity jointly served as the inherent motivations for the superior catalytic performance of Mn/CeO 2 -NC catalyst. During the transient reaction process, no obvious derivatives transformation behavior was observed on CeO 2 -NP-based catalyst, while both E-R and L-H reaction mechanisms occurred on both Mn/CeO 2 -NC and Mn/CeO 2 -NR catalysts. And the Mn/CeO 2 -NC catalyst had the greater transient reaction efficiency than Mn/CeO 2 -NR catalyst at whichever pathways, which might clarify the difference in catalytic activity between Mn/CeO 2 -NC and Mn/CeO 2 -NR catalysts. Finally, the possible reaction mechanism model for low-temperature SCR over Mn-modified different exposed crystal surfaces of CeO 2 catalysts was proposed. No obvious derivatives transformation behavior was observed on CeO 2 -NP-based catalyst during the transient reaction process, while both E-R and L-H reaction mechanisms occurred on Mn/CeO 2 -NC and Mn/CeO 2 -NR catalysts. And the Mn/CeO 2 -NC system catalyst had the greater transient reaction efficiency than Mn/CeO 2 -NR catalyst at whichever pathways, which might clarify the difference of catalytic activity between Mn/CeO 2 -NC and Mn/CeO 2 -NR catalysts. • Mn/CeO 2 -NC catalyst possessed the excellent low-temperature catalytic activity. • Redox property and surface acidity were the inherent motivations of activity. • No obvious derivative transformation behavior was observed on Mn/CeO 2 -NP catalyst. • Both E-R and L-H pathways occurred on Mn/CeO 2 -NC and Mn/CeO 2 -NR catalysts.