Publication costs assisted by Centre National de la Recherche Scientifique XPS studies have been carried out on Ni(OH)2, NiO, and Ni supported catalysts after preparation and after heating or reduction by hydrogen. The precursors of the catalysts were a lamellar clay of nickel antigorite and Ni(OH)2 impregnated at roughly 15 wt % on different high surface area supports such as Ti02, Si02, Si02-Al203, A1203, and MgO. It was observed that transformation of antigorite into NiO supported over amorphous silica led to an increase of 0.5-1.0 eV in the binding energies measured and also a small increase of Ni2+ widths and main peak to satellite splittings. A comparison of the whole range of NiO supported catalysts showed that the binding energies for Ni2+ (XPS and Auger peaks) may vary over a 2-eV range while the hydrogen reduction ease decreased with the following sequence of supports: no support > Ti02 > Si02 ~Si02-Al203 ~A1203 > MgO. The maximum binding energy value reached that of Ni(OH)2 catalyst and it was found, moreover, that the stronger the interaction of NiO with a support, the closer the energy levels to those of Ni(OH)2. Such an effect was interpreted not in terms of definite compounds such as silicate or alumínate at the interface, but rather as due to modification of the electronic properties of NiO which looses its individuality as a Mott insulator, i.e., with a narrow Ni 3d band and undergoes a much larger unpaired spin delocalization toward the support, resulting in larger NiO-to-support interaction. The spectroscopic features of the 2p peaks of Ni2+ (shake-up lines and multiplet splitting effects) have been emphasized and correlated with the ease of reduction. By contrast no interaction between the silica support and metallic nickel particles could be detected no matter what the particle orientation. Agglomeration of NiO and Ni particles at the surface under the given treatment conditions could be determined following the decrease of the ratios of intensities of the Ni to the Si lines and was found to be in very good agreement with electron microscopy data.
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