The design of the highly active NH3-SCR catalyst Ce-W/UiO-66: Close coupling of active sites and acidic sites

Abstract

Ce based catalyst is one of the most important NH3-SCR catalysts. It has been widely recognized that Ce3+ plays a crucial role in NH3-SCR reaction. However, the specific atomic sites for anchoring Ce atoms and the chemical mechanism underlying the formation of Ce3+ in CeO2 are still incompletely known. Herein, we demonstrate that there are abundant hydroxyl groups on the surface of UiO-66, which are the anchoring sites of Ce. As the loading continues to increase, the insufficiently anchored Ce species will agglomerate and induce the formation of Ce3+-rich CeO2 clusters, which served as the redox sites in 10%Ce/UiO-66. On this basis, the strong interaction between W and CeO2 was used to introduce highly dispersed acidic sites (WO3) around CeO2, and thus the redox site and the acidic site are tightly coupled. In situ DRIFTS results revealed that the NH3-SCR reaction pathway followed L-H mechanism on 10%Ce-10%W/UiO-66 catalyst, which is likely to be an important factor for the improved catalytic activity and stability.