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| - Interaction of Pt Clusters with the Anatase TiO2(101) Surface: A First Principles Study
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| - The adsorption of Ptn (n = 1−3) clusters on the defect-free anatase TiO2(101) surface has been studied usingtotal energy pseudopotential calculations based on density functional theory. The defect-free anatase TiO2(101) surface has a stepped structure with a step width of two O−Ti bond distances in the (100) plane alongthe [101̄] direction and the edge of the step is formed by 2-fold-coordinated oxygen atoms along the [010]direction. For a single Pt adatom, three adsorption sites were found to be stable. Energetically, the Pt adatomprefers the bridge site formed by 2 2-fold-coordinated oxygen atoms with an adsorption energy of 2.84 eV.Electronic structure analysis showed that the Pt−O bonds formed upon Pt adsorption are covalent. Amongsix stable Pt2 adsorption configurations examined, Pt2 was found to energetically favor the O−O bridge siteson the step edge along [010] with the Pt−Pt bond axis perpendicular to [010]. In these configurations, oneof the Pt atoms occupies the same O−O bridge site as for a single Pt adatom and the other one either bindsa different 2-fold-coordinated oxygen atom on the upper step or a 5-fold-coordinated Ti atom on the lowerterrace. Three triangular and three open Pt3 structures were determined as minima for Pt3 adsorption on thesurface. Platinum trimers adsorbed in triangular structures are more stable than in open structures. In themost stable configuration, Pt3 occupies the edge O−O site with the Pt3 plane being upright and almostperpendicular to the [001] terrace. The preference of Ptn to the coordinately unsaturated 2-fold-coordinatedoxygen sites indicates that these sites may serve as nucleation centers for the growth of metal clusters on theoxide surface. The increase in clustering energy with increasing size of the adsorbed Pt clusters indicates thatthe growth of Pt on this surface will lead to the formation of three-dimensional particles.
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