CexZr1-xO2 mixed oxide as OSC materials for supported Pd three-way catalysts: Flame-spray-pyrolysis vs. co-precipitation

The three-way catalytic performances of Pd-doped CexZr1-xO2 mixed oxides prepared according to a one pot flame-spray-pyrolysis method and through a two steps preparation where Pd was subsequently impregnated on a commercial CexZr1-xO2 prepared by co-precipitation CZ(COP) were compared. flame-spray-pyrolysis led to bare CexZr1-xO2 CZ(FSP) having higher specific surface area and greater extent of defective sites compared to the co-precipitated sample. Pd incorporation led to drastic gain in activity likely related to the creation of dual sites combining metallic Pd atoms at the vicinity of labile oxygen species from the ceria-zirconia support. However, this peculiar kinetic behavior manifests more extensively on the impregnated Pd/CZ(COP) due to a higher density of metallic Pd sites and a stronger metal-support interaction which weakens the Ce-O bond. Such conclusion agrees with O2-TPD experiments revealing a higher surface oxygen mobility on Pd/CZ(COP) corresponding to higher reactivity of oxygen from the support.