Surface and catalytic properties of CuO andCo3O4 solids as influenced by treatment with Co2+ and Cu2+ species

The effects of treatment CuO and Co3O4 solids with Co2+ and Cu2+ ions on their surface and catalytic properties were investigated using nitrogen adsorption at -196degreesC, the oxidation of CO by O-2 at 100-250degreesC and the decomposition of H2O2 at 30-50degreesC. Pure and doped CuO and Co3O4 Solids were subjected to heat treatment at 300-700degreesC and the dopant concentration was varied between 1.0 and 7.5 mol%. The results obtained revealed that the doping process of the investigated solids increased the degree of crystallinity and particle size of CuO and Co3O4 phases. This treatment led also to a progressive decrease in the specific surface areas (SBET) of the treated adsorbents to an extent proportional to the amount of dopants added. However, doping Of Co3O4 and CuO solids with small amounts of Cu2+ and Co2+ ions, respectively, much increased their catalytic activities in H2O2 decomposition. On the other hand, the doping process brought about both increase and decrease in their catalytic activities towards CO oxidation by O-2 depending on both the nature of the treated solids and that of dopant ions and the calcination temperature. Also, the doping process did not modify the mechanism of the catalytic reactions but changed the concentration of catalytically active sites involved in the catalyzed reactions. (C) 2002 Elsevier Science B.V. All rights reserved.