Submonolayer Vanadium and Manganese Binary Metal Oxides Supported on Three-Dimensionally Ordered Mesoporous CeO2 for Efficient Low-Temperature NH3–SCR

Abstract

Submonolayer-supported catalysts exhibited excellent activity for ammonia selective catalytic reduction (NH3–SCR) and have attracted great interest. Here, a catalyst based on three-dimensional ordered mesoporous (3DOM) CeO2 supported by a submonolayer of vanadium and manganese bimetal oxides (3DOM VOx–MnOx/CeO2) was successfully synthesized. The optimal catalytic temperature was found to shift to lower temperature with increasing VOx–MnOx loading amount under the submonolayer coverage. The 5 wt% 3DOM VOx–MnOx/CeO2 catalyst with submonolayer coverage exhibited the best catalytic performance, achieving a NO conversion of more than 95% at 250 °C. It was found that three-dimensional CeO2 endowed the material with a high specific surface and highly ordered mesoporous channels, which could highly disperse VOx–MnOx below one monolayer coverage. Based on NH3–TPD, H2–TPR, Raman and XPS characterization, an increase in VOx–MnOx content under the submonolayer coverage resulted in an enhancement of the surface acidity, redox capacity, number of oxygen vacancy defects and charge transfer. In particular, the 5 wt% 3DOM VOx–MnOx/CeO2 catalyst showed the highest number of acidic sites that for NH3 activation and the fastest electron transfer required for oxygen to be regenerated. Therefore, the 5 wt% 3DOM VOx–MnOx/CeO2 catalyst with submonolayer coverage generated a significantly enhanced catalytic performance, which made it desirable for NO removal applications.