High-heat treatment enhanced catalytic activity of CuO/CeO2catalysts with low CuO content for CO oxidation

A series of CuO/CeO(2)catalysts with different CuO loadings (0.5, 1, 3, and 5 wt%) were prepared by an impregnation method, and tested for the total oxidation of CO. The samples were characterized by various structural and textural detection techniques including XRD, N(2)sorption, TEM-EDS, H-2-TPR, XPS, andin situDRIFTS. Unexpectedly, the low CuO loading (0.5-3 wt%) samples calcined at high temperature (800 degrees C) exhibited better catalytic performance than those calcined at 500 degrees C, and the catalytic activity gap between the catalysts calcined at 500 degrees C and 800 degrees C shrunk with the increase of copper content. In contrast, when the loading amount of CuO reached a normal value (5 wt%), the CuO/CeO(2)catalyst with low temperature calcination (500 degrees C) obtained a slightly better activity than that calcined at 800 degrees C. The results showed that, for the catalysts with low CuO content (0.5-3 wt%), the higher temperature calcination (800 degrees C) can promote the formation of the coordinatively unsaturated copper atoms and increase the content of active Cu species, resulting in a higher activity than those calcined at 500 degrees C. But this effect was suppressed when the CuO content reached 5 wt%. The coordinatively unsaturated copper atoms, as well as Cu+, were confirmed to be the main active sites of the CuO/CeO(2)catalysts.