Growth of Pt Particles\non the Anatase TiO₂ (101) Surface

Abstract

Growth of Pt_<i>n</i> (<i>n</i> ≤\n37) clusters on the defect-free TiO₂ anatase (101) surface\nhas been studied using ab initio pseudopotential calculations based\non density functional theory. Several initial configurations for clusters\nof 1, 2, 7, 10, and 37 atoms were relaxed to determine the most stable\nstructures. All final optimized structures are three dimensional,\nsuggesting that formation of island-like particles is favored over\nplanar monolayers, as verified experimentally using Pt atomic layer\ndeposition and high-resolution transmission electron microscopy. Diffusion\nbarriers of a single Pt adatom on TiO₂ were calculated\nto understand the mobility of Pt atoms on the TiO₂ surface.\nActivation barriers of 0.86 and 1.41 eV were calculated for diffusion\nalong the [010] and [101̅] directions, respectively, indicating\nthat Pt atoms are relatively mobile along the [010] direction at moderate\ntemperatures. The energy barriers for a Pt atom to escape from an\n11- and a 37-atom Pt cluster on (101) anatase are predicted to be\n1.38 and 2.12 eV, suggesting that particle coarsening occurs by Ostwald\nripening and that Ostwald ripening of deposited Pt particles is limited\nby atom detachment from particles as small as several tens of atoms.