III International Conference

PP-I-70MODIFICATION OF ELECTRONIC STRUCTURE OF METAL NANOPARTICLESBY INTERACTION WITH OXIDE SUPPORTSMikhailov M.N. 2 , Zhidomirov G.M. 1 , Kustov L.M. 2 , Mordkovich V.Z.United Research and Development Centre, Moscow, Russia1 Boreskov Institute of Catalysis SB RAS, Novosibirsk, Russia2 N.D. Zelinsky Istitute of Organic Chemistry, Moscow, RussiaE-mail: mik@ioc.ac.ruFine metal particles supported on various oxides are an important class of catalytic systems.The structure and properties of these catalysts depend on many factors such as the state of thesupport, the procedures used for introduction of the metal component and the conditions of theoxidation-reduction treatments. Oxide surface can strongly affect the degree of dispersion,electronic structure, adsorption and catalytic properties of supported metal nanoparticles. Theaim of the work consists in the determination and analysis of the most important factorsaffecting the electronic structure of Pt nanoparticles supported on various oxides.Pt 6 particles, supported on partially dehydroxylated gamma-alumina, FAU and MFI typezeolites have been studied by the cluster model DFT approach. All calculations were performedwith B3LYP functional along with ECP-31G** basis set. To describe oxides surfaces, a clusterapproach were used. The cluster modeling dehydroxylated alumina surface was derived from thegamma-Al 2 O 3 structure using X-ray diffraction data and was constructed from MgAl 2 O 4 idealspinel unit. The clusters used to simulate MFI and FAU zeolites were obtained directly from theirrespective largest cavities. MFI zeolite was simulated with 20T cluster (19 silicon and onealuminum atoms arranged in two parallel rings). FAU zeolite was represented by a 6T cluster (3silicon and 3 aluminum atoms arranged in 6-member ring). Two main features affecting theelectronic structure of Pt 6 particles were found: basicity of framework oxygen anions and thepresence of the surface hydroxyl groups. The transfer of the hydrogen atoms of hydroxyl groupsonto metal particle (reversed spillover) is observed, accompanied by partial oxidation of metalspecies. The energetic characteristics of this process are evaluated and electron structure andcharge distribution of supported Pt 6 particles discussed. Two factors mentioned above result in theconcurrent electronic density transfer. The hydrogen transfer causes the positive charging of metalparticle, while the interaction with basic sites results in the electron-enriched metal cluster. Thecalculated changes in d-states of Pt particle are in qualitative agreement with earlier describedXAFS experimental data on the supported platinum nanoparticles.132