| 研究実績の概要 |
In this fiscal year, we studied the binding strength of Pd clusters supported on SrO- and TiO2- terminated SrTiO3 (SrO-STO-113 and TiO2-STO-113) perovskite to elucidate the metal support interaction (MSI) of Pd/SrTiO3 catalyst under real three-way catalyst operating condition. We systematically sampled several PdxOy clusters supported on SrO-STO-113 and TiO2-STO-113; as well as PdxOy clusters on gamma-Al2O3 (100) by using machine-learning enhanced global optimization (GOFEE) methods. Oxidation of several small Pd clusters is assessed by atomistic thermodynamics from a set of global minimums of STO-supported PdxOy. Structural properties and interfacial bonding were evaluated in detail. The square-planar PdO4 motif is found to be an elementary building block of oxidized clusters. We found that small metallic Pd clusters with an oxygen vacancy at the substrate underneath is stable under the reductive atmosphere, while PdO-like clusters are stable under stoichiometric and oxidative ones. We find that the MSI is further increased upon the oxidation of Pd clusters on both STO and gamma-Al2O3 surfaces, implying that the oxidative pretreatment will increase the thermal stability of the TWC. Moreover, compared with conventional gamma-Al2O3, MSI of small PdxOy clusters and STO (001) surfaces is much stronger driven by greater charge transfer interaction. The growth of small oxidized PdxOy clusters is also studied and some “magic” numbers in term of stability against the Otsward ripening are found. Our results indicate Pd/STO catalysts has higher thermal stability.
|
