Highly enhanced soot oxidation activity over 3DOM CoO-CeO catalysts by synergistic promoting effect.

Three-dimensionally ordered macroporous (3DOM) CoO-CeO catalysts with controllable Co/Ce molar ratios synthesized by colloidal crystal template method were developed to catalyze the NO-assisted soot oxidation for the first time, and the obtained 3DOM CoO-CeO catalysts exhibited highly enhanced soot oxidation activity. Detailed characterizations of 3DOM CoO-CeO 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 Co reactive sites, the surface enrichment of Ce species and the improved redox properties. Meanwhile, the high NO storage and oxidation capacity resulted from the integrated respective merits of CoO and CeO also accounted for the enhanced soot oxidation activity via NO-assisted mechanism. Furthermore, the 3DOM CoO-CeO 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.