A rapid microwave-assisted solution combustion synthesis of CuO promoted CeO2–MxOy (M = Zr, La, Pr and Sm) catalysts for CO oxidation
A series of copper oxide promoted CeO2–MxOy (MxOy = ZrO2, La2O3, Pr2O3 and Sm2O3) mixed oxides were synthesized by microwave-assisted solution combustion method using urea as the fuel and the respective metal nitrates as the precursors. The physico-chemical properties of the synthesized materials were analysed by BET surface area, X-ray diffraction (XRD), Raman spectroscopy, temperature programmed reduction/oxidation (TPR/TPO), X-ray photoelectron spectroscopy (XPS) and oxygen storage capacity (OSC) methods. XRD measurements confirmed the formation of solid solutions between ceria and the doped metal oxides in the presence of copper promoter. Raman measurements suggested defective structure of the mixed oxide solid solutions resulting in the formation of oxygen vacancies. The TPR/TPO studies revealed that the reduction behaviour of ceria depends on the type of metal dopant. XPS studies confirmed the presence of cerium in both Ce3+ and Ce4+ oxidation states in all mixed oxides. All the doped mixed oxides exhibited better CO oxidation activity compared to the undoped copper–ceria catalysts. Among various samples, ZrO2 doped copper–ceria showed a high activity (T1/2 ∼ 378 K) followed by samarium, praseodymium and lanthanum oxide doped samples, respectively. Significance of the combustion synthesis method has been addressed that include simplicity, flexibility and the control of different favourable factors.
Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (284 K)Download as PowerPoint slideHighlights► Designed active CO oxidation catalysts by microwave-induced combustion synthesis. ► Incorporation of various dopants enhanced CO oxidation activity of copper–ceria. ► The addition of dopants resulted in improved textural/structural properties. ► Mixed oxides are more active than single oxides due to synergetic effects. ► Zirconium doped copper–ceria exhibited superior CO oxidation activity.
Journal: Applied Catalysis A: General - Volumes 445–446, 28 November 2012, Pages 297–305