Abstract

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−Ce0.7Zr0.3Ox 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 Pdn+/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.

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