A comparative study of CO oxidation over Cu-O-Ce solid solutions and CuO/CeO ₂ nanorods catalysts

The distribution of copper species (on the surface or in the bulk of CeO ₂ support) and the interfacial interactions between CuO and CeO ₂ are critical in understanding the synergistic effect on the catalytic activity of CeO ₂ supported CuO catalysts. In this report, Cu-O-Ce solid solutions and CuO impregnated on CeO ₂ nanorods catalysts (CuO/CeO ₂ ) with various compositions were prepared using thermal decomposition and hydrothermal methods, to understand the distribution effect of copper species on low temperature CO oxidation. The incorporation of copper ions into CeO ₂ lattice in both types of catalysts was confirmed by X-ray diffraction (XRD), Raman spectroscopy, and hydrogen temperature programmed reduction (H ₂ -TPR) analysis, indicating a strong CuO-CeO ₂ interfacial interaction and formation of oxygen vacancies which compensates the charge difference between copper (I/II) and cerium (III/IV) ions. A series of temperature programmed reduction-temperature programmed oxidation (TPR-TPO) thermal cycling studies were conducted to understand the interactions between three assigned copper species (α, β, and γ) with CeO ₂ support and the corresponding catalytic performance of the catalysts. In addition, an improved low temperature catalytic performance for the CuO/CeO ₂ nanorods catalysts was observed, which was attributed to stronger interactions between copper species and CeO ₂ nanorods enriched with surface defects (steps and voids etc.).