Promoting effect of CeO<SUB>2</SUB> in combustion synthesized Pt/CeO<SUB>2</SUB> catalyst for CO oxidation

A 1% Pt/CeO2 catalyst prepared by the solution combustion method shows a higher catalytic activity for CO oxidation by O2 compared to Pt metal particles. At least six hydrogen atoms are taken up per Pt at -25 &#176;C. The structure of 1% Pt/CeO2 catalyst has been investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR) spectroscopy. Rietveld refinement shows that Pt ions are incorporated into the CeO2 matrix in the form of Ce1-xPtxO2-&#948; solid solution. A decrease in oxygen content in 1% Pt/CeO2 is seen in relation to pure CeO2. TEM studies show that Pt is dispersed as atoms or ions and only a small amount as Pt metal particles. The Pt(4f) core level region in XPS shows that Pt is present mostly in the Pt2+ ionic state on CeO2 surface. FTIR of 1% Pt/CeO2 shows a strongly adsorbed CO peak at 2082 cm-1 corresponding to oxidized Pt. These structural studies show that Pt ions in the catalyst are substituted for Ce4+ ions in the form of Ce1-xPtxO2-&#948;, creating oxide ion vacancies leading to a strong Pt2+-CeO2 interaction that is responsible for higher catalytic activity