The effect of CeO2 on the dynamics of Pd–PdO transformation over Pd/Al2O3 combustion catalysts

The efficiency of PdO-based catalysts for the combustion of methane is strongly influenced by the dynamics of Pd–PdO transformation. Previous investigations reported that the addition of CeO2 to the support results in a strong promotion of Pd reoxidation. In this work it is shown that the mechanism of Pd–PdO transformation in redox cycles in the presence of CeO2 is associated with a deep contact between the noble metal crystallites and CeO2: only Pd particles in contact with the promoter reoxidize at high temperature, while a different dynamics characterizes the behaviour of Pd particles not in contact with CeO2.