Metal-Support Interaction at Palladium-Composite Manganese Oxide Interface and CO Oxidation Activity

Abstract

Pd-loaded perovskite composite manganese oxide (Pd/AMnO₃, A = Ca, Sr, La) catalysts were prepared by coprecipitation method, in order to reveal metal-support interaction (MSI). Particulate PdO with sizes of a few ten nanometers were randomly formed on CaMnO₃. On the other hand, fibrous PdO with diameter approximately 20 nm was formed on LaMnO₃. Both shape of PdO were formed on SrMnO₃. HAXPES measurement showed a down shift of valence band of deposited PdO depending on the composite manganese oxide. Our characterization indicates that the MSI at Pd–AMnO₃ interface affects not only the shape but the electronic structure of deposited PdO on AMnO₃. The CO oxidation activity was in order of Pd/LaMnO₃ > Pd/SrMnO₃ > Pd/CaMnO₃, which corresponds to the order of the PdO valence band shift trend. We proposed that the observed correlation between the valence band shift and the CO oxidation activity for Pd/AMnO₃ can be understood in terms of the CO adsorption strength.

Metal-support interaction at Pd-composite manganese oxide AMnO₃ (A = Ca, Sr, La) interface is effective to promote CO oxidation.