The role of method of preparation of CuO–NiO system on its physicochemical surface and catalytic properties

The effects of method of preparation of CuO–NiO system on its surface, textural and catalytic properties were investigated. The system investigated was prepared by four different methods namely, sol–gel (SG), hydrothermal (HY), wet impregnation (IMP) and laser vaporization controlled condensation (LVCC). The extent of CuO was fixed at 20 mol% CuO in all prepared catalysts. This percentage of CuO was found to result in a maximum catalytic performance. The techniques employed were XRD, EDX, TEM, surface excess oxygen, nitrogen adsorption at −196 °C and catalytic oxidation of CO by O2 at 120–260 °C using both static and flow methods. The results revealed that all catalyst samples prepared by the different adopted methods existed as nanocrystalline solids measuring a crystallite size varying between 9 and 45 nm. The solid prepared by LVCC method measured the smallest crystallite size and the biggest specific surface area and catalytic activity. On the other hand, the solid prepared by HY method measured the biggest crystallite size and the smallest specific surface area and catalytic activity. Indeed, the sample prepared by LVCC method showed the maximum amount of surface excess oxygen while the solid obtained by HY method exhibited the minimum amount of surface excess oxygen.