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The effect of the Pd-support interface on the dynamic oxygen storage capacity (DOSC) and three-way catalytic activities were investigated using Pd chromatographically distributed between Ce 0.7 Zr 0.3 O 2 and Al 2 O 3 . CO-He pulse, H 2 -TPR, and XPS show that the Pd-(Ce, Zr) Ox interface promotes a higher degree of oxygen releasing than the Pd-(Al 2 O 3 ) interface while maintaining the oxidized states of Pd. Pd promotion at the Pd-(Ce, Zr) Ox interface depends on the oxygen species of ceria-zirconia, and promotion takes place on surface oxygen and subsurface oxygen species. Dynamic CO-O 2 transient measurement shows that DOSC is greatly promoted by the Pd-(Ce, Zr) Ox interface. The transient results indicate that the Pd-(Ce , Zr) Ox interface accelerates the oxygen spillover and back-spillover between Pd and the support oxide, but this phenomenon is not obvious for the Pd-(Al 2 O 3 ) interface. Higher CO oxidation activity was obtained over a catalyst with a higher degree of Pd-(Ce, Zr) Ox interface in proportion to its DOSC performance. A two-step CO oxidation mechanism at the Pd-(Ce , Zr) Ox interface includes oxygen migration and its reaction with the adsorbed CO. Higher NO reduction and C 3 H 8 oxidation rates were obtained with a catalyst with more Pd-(Al 2 O 3 ) interface, showing negative correlation with the DOSC performance.

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Effects of Pd-supported interactions toward redox behaviors concerning three-way catalytic reactions and oxygen-buffering effects are investigated through stepwise changing Pd-loading locations over ceria−zirconia and alumina. Through light-off tests and kinetics, texture, and surface studies, discrepant but redistributable Pd−A2O3 and Pd−Ce0.7Zr0.3O x interfaces are defined and analyzed. Pd species are inclined to promote the transformation of Ce4+ to Ce3+ and maintain themselves as fine particles on ceria−zirconia surfaces. Oxygen spillover promoted by Pd n+/Pd0−Ce4+/Ce3+ redox couples benefits the oxygen-buffering effect, but is limited by the increase of reaction temperatures and ceria−zirconia reducibility. This strong oxidative interaction overcomes the possibility of ceria-related anionic vacancies in facilitating NO dissociation and, thus, improves CO conversion only. Stochiometric light-off tests show higher activities for NO reduction and C3H8 oxidation on a Pd−Al2O3 interface, where the different morphologies and redox states of Pd-supported interfaces should be the main contributing factors for efficient molecular bond dissociation.