CuO/MgO Nanocomposites by Wet Impregnation: An XPS Study

Two copper oxide/magnesium oxide nanocomposite powders were prepared by wet impregnation of nanosized magnesia powders. The supporting magnesia was formed by precipitation through the addition of tetraethyl ammonium hydroxide to magnesium nitrate. The samples are characterized by a nominal (i.e. calculated from the weighted amount of precursors) Cu/Mg atomic ratios of 0.01 or 0.5. The surface properties and the influence of the Cu/Mg atomic ratio are investigated by means of XPS (using an Al Kα x-ray source). In addition to the wide scan spectra, detailed spectra for the Mg 1s, Cu 2p, and O 1s regions and related data are presented and discussed. XPS analysis confirms the presence of MgO and CuO; the peak shapes are consistent with a more heterogeneous chemical environment for the sample with lower Cu/Mg atomic ratio. In both cases, the measured Cu/Mg atomic ratio is less than nominal concentration suggesting that there is diffusion of Cu inside the support. The O/(Mg+Cu) atomic ratio decreases with increasing Cu/Mg and is higher than the nominal one confirming the surface hydroxylation.