Influence of particle morphology on catalytic performance of CeO₂/ZrO₂ for soot oxidation

Abstract

The effect of size and morphology of CeO₂/ZrO₂ catalysts, prepared by impregnation [CZ(IMP)], coprecipitation [CZ(CP)] and deposition–precipitation [CZ(DP)] methods, on the soot oxidation performance was investigated. TEM observation revealed that CeO₂ particles are well dispersed with the size of 10 nm on ZrO₂ support for CZ(IMP). In case of CZ(CP), the agglomeration of CeO₂–ZrO₂ solid solution particles was recognized. On the other hand, large CeO₂ particles (50 nm) were independently present in CZ(DP). Soot oxidation activity of CeO₂/ZrO₂ was strongly dependent on the morphology of CeO₂ particles and decreased in the order of CZ(IMP) > CZ(CP) > CZ(DP). From isotopic transient kinetics analysis using ¹⁸O₂, the lattice oxygen in the surface region of CeO₂ particles in CZ(IMP) was highly reactive compared with those in the surface and bulk of CeZrO_x solid solution in CZ(CP), resulting in high soot oxidation activity.