| Abstract
| - The catalytic combustion activity of PdPt bimetallic catalysts is governed by oxide phases which form under oxygen-rich operation conditions. We investigate the thermodynamic stability of mixed PdxPt1−xOy phases with the crystal structures of PdO, PtO2, and Pt3O4 within an ab initio thermodynamics framework based on density-functional theory calculations. Our results suggest a complex mixing−demixing behavior of the Pd−Pt−O system upon variations of temperature and oxygen partial pressure. At atmospheric pressure mixed oxides are predicted to be stable only at temperatures below 400−500 K, whereby the presence of Pd4+ ions is stabilized with increasing Pt amount in a PdxPt1−xO2 phase. At intermediate temperatures a mixture of phases becomes stable where PdO coexists with PtO2 or Pt3O4. At high temperatures the oxides decompose directly to form PdPt alloys, except for Pd-rich systems, where PdO and metallic Pt coexist within a small temperature window.
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