OP-II-3

OP-I-5where ∗ and ∗ vare the active centers of the surface and subsurface layers,respectively. CO can adsorb both over the surface of particle and the support(desorption coefficient of CO ads from the support was assumed several times higherthan that from the Pd particle) and then diffuse through the support (intensity ofdiffusion was assumed several times higher than that over the Pd particle) to the Pdparticle; oxygen can adsorb only on the available centers of the palladium particle,preferably on the terraces.The influence of both reaction parameters (rate coefficients and diffusionintensity) and particles characteristics (size, degree of roughening, etc.) on theoscillation behavior and pattern formation has been studied. Decreasing of theparticles size to less than ~ 30×30 active centers (depending on the chosen set ofparameters) leads to the disappearing of oscillations. The reasons for thisphenomenon are the following: (i) decreasing of the particles size leads to theroughening (increasing of the defects concentration) of its surface and, hence, to thedeficit of the available centers for oxygen adsorption; (ii) the influence of theadditional flux of CO ads from the perimeter shifts the interval of oscillations to thehigher values of the oxygen partial pressures. The presence of CO ads spilloverdetermines the character of concentration waves over the surface of Pd nanoparticle– oxygen wave propagates from the central region of the particle to the perimeter,and the CO ads wave moves from the perimeter, always enriched by CO ads , to thecentre of the particle. In the case when the collection zones [6,7] overlap (the densityof the particles on the support is high) the synchronization of oscillations betweenneighboring oscillators (nanoparticles) due to CO ads diffusion over the support seemsto be possible. The presence of CO ads spillover over the support can manifest assize-dependent reactivity of the supported catalysts.References[1]. Zhdanov V.P., Kasemo B. Surf. Sci. Rep., 2000, 39, 25-104.[2]. Zhdanov V.P. Surf. Sci., 2002, 500, 966-985.[3]. Elokhin V.I., Myshlyavtsev A.V. In: Dekker Encyclopedia of Nanoscience and Nanotechnology, 2nd Ed.,Vol. II. C.I. Contescu and K. Putyera, Eds.; Taylor & Francis: New York, 2009; pp. 782-793.[4]. Latkin E.I., Elokhin V.I., Matveev A.V., Gorodetskii V.V. J. Molec. Catal. A, Chemical, 2000, 158,161-166.[5]. Kovalyov E.V., Elokhin V.I., Myshlyavtsev A.V. J. Comput. Chem., 2008, 29, 79-86.[6]. Henry C.R. Surf. Sci. Rep., 1998, 31, 231-325.[7]. Boudart M. Topics in Catalysis, 2000, 13, 147-149.Acknowledgements This work was supported by the RFBR Grant # 08-03-00454.46