Table II

A: Effect of Metal Addition on the Reduction of CeO2, as Determined from the Surface (plus near surface) O to Ce Atomic Ratios
Catalyst at.% M O(1s)/Ce(3d) = x ΔO = 2 − x ΔO/at.% M
Pd/CeO2 0.25 1.76 0.24 0.96
Pt/CeO2 0.26 1.59 0.41 1.58
Rh/CeO2 0.17 1.91 0.09 0.53
Au/CeO2 0.19 2.32 −0.32 −1.68
Pt–Pd/CeO2 Pt = 0.38; Pd = 0.45 1.51 0.49 0.59
Au–Rh/CeO2 Au = 0.27; Rh = 0.57 1.49 0.51 0.61
Pt–Rh/CeO2 Pt = 0.21; Rh = 0.21 1.66 0.34 0.81
B: State of Metal Ions on CeO2 in the ‘As Prepared’ Catalysts
Catalyst Binding Energy, eV, XPS Assignment
Pd/CeO2 Pd(3d5/2) = 336.5 PdO
Pt/CeO2 Pt(4f7/2) = 74.0 PtO
Rh/CeO2 Rh(3d5/2) = 309.5 RhO2
Au/CeO2 Au(4f7/2) = 85.6 Au2O3
Pt–Pd/CeO2 Pd(3d5/2) = 337.5;
Pt(4f7/2) = 73.0
Au–Rh/CeO2 Rh(3d5/2) = 308.7;
Au(4f7/2) = 85.5
Pt–Rh/CeO2 Rh(3d5/2) = 309.5;
Pt(4f7/2) = 73.0