Structure and reactivity of zero-, two- and three-dimensional Pd supported on SrTiO3(001)

a r t i c l e i n f o Keywords: Supported Pd nanoparticles Particle–substrate interaction Density functional calculation Molecule adsorption on particle Strontium titanate substrate Interactions of Pd atoms, films and nanoparticles with a SrTiO 3 (001) substrate are studied via first principles Density Functional Theory. Effects of the substrate upon structural, electronic and chemical properties of the supported Pd are considered. By comparison of different experimentally observed particle shapes and orientation, and with atomic and planar Pd adsorbates, some detailed understanding is obtained about particle–support interactions. Adsorption of atoms (H, C, O) and small molecules (OH, CO, CH 3) is used as a probe of chemical activity of different faces, edges and vertices of the particles. Metallic nanoparticles supported on refractory oxides are known to be useful catalysts, especially for oxidation of organic molecules. Particle–support interactions have been shown to contribute to catalyst performance by stabilizing particle size and dispersion, as well as controlling chemical selectivity and reactivity. There appears to be a consensus that the presence of specific particle facets, edges and vertices is beneficial, perhaps essential to both catalytic selectivity and activity. With respect to particle–substrate interaction, one frequently speaks of the importance of 'triple-points' at the intersection of catalytic particle, its support, and the gas phase medium conducting reactive molecules. Seen as a composite, the particle–oxide interface can provide catalytic sites not available in either component separately. As a recent example, the epitaxial match between Pt(110) and the (100) crystal plane of SrTiO 3 (STO) has been shown to impart exceptional stability and preferred metal surface orientation to Pt nanoparticles produced by Atomic Layer Deposition (ALD) on both crystal surfaces and nanocubes [1,2]. High resolution electron microscopy has shown detailed shapes and facets of Pd nanoparticles, which depend upon temperature and growth conditions, as well as the stage of reconstruction of the STO surface [3]. Further work on Ag:STO(100) shows the generality of growth and stability over a number of catalytically important metals [4]. The present work is dedicated to theoretical modeling and analysis which could elucidate specific aspects of particle–substrate interactions and their impact on gas-phase adsorption of atoms and small molecules. The ability to understand and control these interactions , along with surface preparation such as partial hydroxylation, could lead to optimized catalytic properties. Space does not permit an adequate review of the rich theoretical and experimental literature on Pd particles, films, …