Growth of Pt Particles on the Anatase TiO2 (101) Surface

Growth of Pt-n (n <= 37) clusters on the defect-free TiO2 anatase (101) surface has been studied using ab initio pseudopotential calculations based on density functional theory. Several initial configurations for clusters of 1, 2, 7, 10, and 37 atoms were relaxed to determine the most stable structures. All final optimized structures are three dimensional, suggesting that formation of island-like particles is favored over planar monolayers, as verified experimentally using Pt atomic layer deposition and high-resolution transmission electron microscopy. Diffusion barriers of a single Pt adatom on TiO2 were calculated to understand the mobility of Pt atoms on the TiO2 surface. Activation barriers of 0.86 and 1.41 eV were calculated for diffusion along the [010] and [10 (1) over bar] directions, respectively, indicating that Pt atoms are relatively mobile along the [010] direction at moderate temperatures. The energy barriers for a Pt atom to escape from an 11- and a 37-atom Pt cluster on (101) anatase are predicted to be 1.38 and 2.12 eV, suggesting that particle coarsening occurs by Ostwald ripening and that Ostwald ripening of deposited Pt particles is limited by atom detachment from particles as small as several tens of atoms.