Copper-ceria sheets catalysts: Effect of copper species on catalytic activity in CO oxidation reaction

Copper-ceria sheets catalysts with different loadings of copper (2 wt.%, 5 wt.% and 10 wt.%) supported on ceria nanosheets were synthesized via a deposition-precipitation (DP) method. The prepared catalysts were systematically characterized with various structural and textural detections including X-ray diffraction (XRD), Raman spectra, transmission electron microscopy (TEM), X-ray absorption fine structure (XAFS), and temperature-programmed reduction by hydrogen (H-2-TPR), and tested for the CO oxidation reaction. Notably, the sample containing 5 wt.% of Cu exhibited the best catalytic performance as a result of the highest number of active CuO species on the catalyst surface. Further increase of copper content strongly affects the dispersion of copper and thus leads to the formation of less active bulk CuO phase, which was verified by XRD and H-2-TPR analysis. Moreover, on the basis of in-situ diffuse reflectance infrared Fourier transform spectroscopy (in-situ DRIFTS) results, the surface Cu+ species, which are derived from the reduction of Cu2+, are likely to play a crucial role in the catalyzing CO oxidation. Consequently, the superior catalytic performance of the copper-ceria sheets is mainly attributed to the highly dispersed CuOx cluster rather than Cu-[O-x]-Ce structure, while the bulk CuO phase is adverse to the catalytic activity of CO oxidation. (c) 2017 Published by Elsevier B.V. on behalf of Chinese Society of Rare Earths.