Roles of cobalt and cerium species in three-dimensionally ordered macroporous CoxCe1-xOδ catalysts for the catalytic oxidation of diesel soot.

Three-dimensionally ordered macroporous (3DOM) CoxCe1-xOδ oxides with different Co/Ce atomic ratios were synthesized by a colloidal crystal template (CCT) method. They show higher activity for soot combustion in O2 than single CeO2 and Co3O4 under loose contact conditions. XRD, Raman, XPS, H2-TPR and soot-TPR characterizations were carried out to study the surface and bulk oxygen vacancies and to correlate them to the activity. There exists electron transfer from Ce to Co in the matrix. Both Ce3+ and Co2+ species contribute importantly to the creation of surface and bulk oxygen vacancies, which determine the ignition and burnout temperatures of the catalysts, respectively.