Copper and copper oxides (Cu2O and CuO) have been deposited by evaporation of copper and subsequent oxidizing treatments, on the surface of flat SiO2 and ZrO2 substrates. Large variations of several eVs have been found in the values of the Cu 2p3/2 binding energy (BE) and Auger parameter (α‘) of copper as a function of the amount of deposited metallic copper or copper oxides. The magnitude of the changes was also dependent on the type of support upon which the experiment was carried out. These changes have been attributed to modifications in the factors contributing to the initial and final state effects of the process, according to the dispersion degree and the nature of the interactions between the copper oxide moieties and the support. All of these changes can be systematized with the help of chemical state plots. Experiments carried out with real catalysts stress the need of such plots, which summarize the results obtained with the model systems, for a proper characterization of the supported oxide phases in this kind of real materials.

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The effect of a reduction process with CO or H 2 on the size of nickel particles in Ni/ZrO 2 dry methane reforming catalysts have been studied by means of in situ X-ray Absorption Spectroscopy (XAS) and Diffuse Reflectance FTIR Spectroscopy (DRIFTS). Our results clearly indicate that a high temperature treatment with CO increases the dispersion of the nickel metallic phase. XAS results have shown a lower coordination number of Ni in the sample treated with CO than that reduced with H 2 . From the DRIFTS results, it can be established that, under the CO treatment, the formation of Ni(CO) 4 complexes corrodes the nickel particles, decreasing their size. The formation of these gas molecules occurs without measurable losses of nickel from the catalyst which maintains the same nickel content after the hydrogen or the CO treatment at high temperature. Therefore, this airborne nickel compound, by colliding with the zirconia surface, must deposit the nickel metal atoms around onto the support. This behavior is evidence of an important interaction between nickel and zirconia surface as unlike other supports there is no losses of nickel during the dispersion process on zirconia. Although different effects of CO on nickel catalysts have been previously described, we have found for the first time several experimental evidences demonstrating the whole redispersion phenomenon.