The behavior of a series of CeO2 catalysts in soot combustion reaction was investigated by HRTEM and
XPS. It is shown that nanodomains of reduced ceria in the form of Ce6O11 develop during reaction under
oxygen-containing atmosphere, supporting the idea that the reaction between CeO2 and carbon
particulate results in the formation of a reduced ceria phase. The fact that oxygen-deficient cerium oxide
particles are not in contact with soot, whereas regular CeO2 particles are also found in contact with
particulate, may suggest that reaction with soot implies the extraction of oxygen from the CeO2 fluorite
lattice, confirming the importance of redox mechanism in ceria-catalyzed soot oxidation.
