Thermal H2-treatment effects on CO/CO2 conversion over Pd-doped CeO2 comparison with Au and Ag-doped CeO2

Abstract

CO oxidation to CO2 by Pd–CeO2 catalysts was tested by temperature-programmed mass spectrometry for as-prepared and thermal H2-treated Pd-doped CeO2 catalysts, compared with those of Ag and Au-doped CeO2. For the as-prepared samples, the oxidation rate and the T10 % (the temperature at 10 % CO conversion) occurred in the order of Au ≈ Pd > Ag ≫ undoped in the 1st CO oxidation run, while in the 2nd run, the order became Au > Pd > Ag ≫ undoped. For the thermal H2-treated samples, the order became Pd > Au > Ag > undoped and Au > Pd > Ag > undoped in the 1st and 2nd CO oxidation runs, respectively. The T10 % in the 2nd run commonly occurred at much lower temperatures for the metal-doped CeO2 upon achieving good metal-oxide interfacial contact during the 1st run. The T10 % of undoped CeO2 was the most significantly affected by the thermal treatment effects while those of metal-doped CeO2 catalysts were not greatly affected by the thermal H2-treatment. Based on these findings, the metal-support interaction/interface is more important than the surface area, Au (88 m2/g) > Ag (59 m2/g) ≈ Pd ≈ undoped.