High-temperature calcination enhances the activity of MnOx catalyst for soot oxidation
Abstract
High-temperature calcination usually induces the sintering of catalysts, thus resulting in negative effects on their performance. However, in this study we surprisingly found that high-temperature calcination could enhance the activity of MnOx catalysts for soot oxidation. Combined experimental and theoretical analysis revealed that high-temperature calcination of MnOx (900 oC) could induce the generation of more oxygen defects, due to the transformation of α-MnO2 to δ-MnO2 and Mn2O3, with lower formation energy for oxygen defects. The generated oxygen defects would facilitate activation of surface chemisorbed oxygen, producing more active oxygen species, which can further oxidize NO to NO2 to accelerate soot combustion. Therefore, the MnOx calcinated at 900 oC exhibited much higher activity for soot oxidation than that calcinated at 500 oC. This study provides significant insight into the effects of calcination temperature on MnOx catalysts, thereby aiding in the design of high-efficiency catalysts for the control of soot emission.