Cu-Ce-La-Ox as efficient CO oxidation catalysts: effect of Cu content

Nanograins of Ce-La-xCu-O oxides, of 16 nm2 area size, are tested as materials towards the CO oxidation . Preservation of the cubic lattice structure following La3+ and Cu2+ metal cations doping is confirmed based on the powder X-ray diffraction and Raman studies. From XPS, the presence of mixed Ce3+/Ce4+ and Cu2+/Cu1+ oxidation states was confirmed, which was more profound in the low Cu-content Ce-La-xCu-O catalysts. Cu increases the concentration of oxygen vacant sites in the doped-CeO2 according to the Raman intensity ratio IOv/IF2g of 1.58 and 1.78 with the increase in copper content from 7 to 20 at.% as compared to the lower value of 0.44 for the Ce-La. The mobility of the surface and bulk lattice oxygen is further investigated using 16O/18O isotopic exchange (TIIE), and is found to be Cu at.% dependent. For the case of Ce-La-20Cu, the participation of the lattice oxygen (OL) in the reaction mechanism has been demonstrated using transient experiments. Accordingly, the specific rate (μmol CO m-2s-1) of the CO oxidation reaction is found to be higher for the Ce-La-20Cu and Ce-La-7Cu catalysts, corroborating thus the presence of more mobile/labile oxygen species in those ternary catalysts as opposed to the other lower copper compositions