III International Conference

PP-I-69NEW POSSIBILITIES OF THE XPS METHOD APPLIED TO Ru/MgO SYSTEMSLarichev Y.V., Malykhin S.E.Boreskov Institute of Catalysis SB RAS, Novosibirsk, RussiaE-mail: larichev@catalysis.ruIt is widely accepted that nanosize properties are due to high surface/bulk atom ratios.The surface to bulk atoms ratio changes significantly with nanoparticle size. Since theelectronic structure of surface atoms greatly differs from the bulk ones, the overall propertiesof nanoparticles are also different. A straightforward way to detect these particular changes isXPS spectroscopy due to its ability to gain deep into the electronic structure of atoms: fromcore to valence atomic energy levels. The shortcoming of this approach is due to the overallXPS spectrum is an average of many individual ones. In most cases it is almost impractical toobtain samples of uniform size nanoparticles. This difficulty should be considered as the mainobstacle in a way to get well-calibrated XPS technique, which is in principle able todistinguish the particle sizes and morphology.Ab initio quantum chemical methods allow one to solve this problem. Calculated DOS(density of states) spectrum is usually in good confinement with real XPS spectrum, and italso can be correctly expanded in terms of localized density of states (LDOS) related to somesort of atoms, for example, surface atoms. The reconstruction of total density of states fromarbitrary chosen LDOSes to simulate various surface/bulk ratios effects becomes possible.Here we report some preliminary results of the XPS investigation applied to Ru/MgOsystem. The Ru/MgO samples were prepared via the incipient wetness impregnation of MgOwith acetone solution of the ruthenium complexes at the room temperature. The reduction wascarried out by the H 2 stream together with sample heating up to 450°C. According to XRDand TEM data, the most part of Ru was 3-30 nm nanoparticles. Two narrow bands additionalto wide metallic-character Ru-band were found in XPS difference spectra at 4.1 and 7.1 eV.The origin of these bands was established with the aid of ab initio calculation of RuO 2 andbulk Ru DOS. The bands were assigned to the RuO 2 species. Thus, the existence of small Ruoxide particles stabilized in the Ru/MgO systems was proved.131