CO oxidation activity enhancement of Ce0.95Cu0.05O2−δ induced by Pd co-substitution
A bimetallic, ionic, Ce0.93Pd0.02Cu0.05O2−δ catalyst was synthesized in one step using a urea-assisted solution combustion method. The structural and electronic properties of the catalyst were studied by different techniques together with those of mono-metallic analogues. The catalytic performance of the materials was investigated using CO oxidation as the model exhaust reaction and the nature of the active sites was examined by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). X-ray diffraction (XRD), Raman spectroscopy, XPS, XANES, EXAFS and high resolution transmission electron microscopy (HR-TEM) revealed that the prepared materials are single-phase, solid-solution oxides with a fluorite structure. In situ XRD studies showed that the prepared materials are metastable up to 1100 °C. The correlation of the characterization and catalytic results indicates that catalytic performance is influenced by the presence of oxygen vacancies and the existence of synergism between Pd2+, Cu2+ and cerium ions. DRIFTS results revealed that CO interacts with the active centres already at room temperature, forming Cu+ and Pd2+ carbonyls.