Study of the influence of the Cu/Ce loading ratio in the formation of highly active species on ZrO₂ supported copper-ceria catalysts

This work studies the effect of different Cu/Ce loading ratios in the formation of highly dispersed copper species being interacting with CeO₂ on zirconia-supported CuO–CeO₂ catalysts. These species have a strong effect on the CO oxidation reaction and for this reason such reaction was selected to conduct the present study. Catalysts with different metal loads were prepared by the co-impregnation method of Cu and Ce nitrates on ZrO₂ support. It was found that the influence of the two metals occurs cooperatively. The type of copper species formed on the ZrO₂ support depends on the Cu and Ce loads, with the existence of an optimum in activity when the Cu/Ce loading ratio being around 0.5. The incorporation of CeO₂ increases the dispersion capacity of ZrO₂ and facilitates the reduction of surface CuO species. Maintaining the Cu/Ce loading ratio constant at the optimal ratio (0.5) and increasing the total metal load (Cu+Ce) gave no significant increase in the catalytic activity above 6%. The latter suggests that higher metal loadings (Cu+Ce) does not lead to an increment of highly dispersed copper species interacting with CeO₂, which is the most active species on the surface of this catalysts.