Highly enhanced soot oxidation activity over 3DOM Co3O4-CeO2 catalysts by synergistic promoting effect.

Abstract

Three-dimensionally ordered macroporous (3DOM) Co3O4-CeO2 catalysts with controllable Co/Ce molar ratios synthesized by colloidal crystal template method were developed to catalyze the NOx-assisted soot oxidation for the first time, and the obtained 3DOM Co3O4-CeO2 catalysts exhibited highly enhanced soot oxidation activity. Detailed characterizations of 3DOM Co3O4-CeO2 catalysts revealed that the highly enhanced soot oxidation activity was originated from the synergistic promoting effect by combining the macroporous effect resulted from the unique 3DOM framework, the chemical nature associated with more Co3+ reactive sites, the surface enrichment of Ce species and the improved redox properties. Meanwhile, the high NOx storage and oxidation capacity resulted from the integrated respective merits of Co3O4 and CeO2 also accounted for the enhanced soot oxidation activity via NOx-assisted mechanism. Furthermore, the 3DOM Co3O4-CeO2 catalysts demonstrated strong stability because of the surface enrichment of Ce species improving the thermal stability and the robust 3DOM framework inhibiting the structural collapse, showing their potential applications under practical conditions.