Growth mechanism of palladium clusters on rutile TiO2(110) surface

Oxide-supported transition metal systems have been the subject of enormous interest due to the improvement of catalytic properties relative to the separate metal. Thus in this paper, we embark on a systematic study for Pd_n (n = 1–5) clusters adsorbed on TiO₂(110) surface based on DFT-GGA calculations utilizing periodic supercell models. A single Pd adatom on the defect-free surface prefers to adsorb at a hollow site bridging a protruded oxygen and a five-fold titanium atom along the [110] direction, while Pd dimer is located on the channels with the Pd-Pd bond parallel to the surface. According to the transition states (TSs) search, the adsorbed Pd trimer tends to triangular growth mode, rather than linear mode, while the Pd₄ and Pd₅ clusters prefer three-dimensional (3D) models. However, the oxygen vacancy has almost no influence on the promotion of Pd_n cluster nucleation. Additionally, of particular significance is that the Pd-TiO₂ interaction is the main driving force at the beginning of Pd nucleation, whereas the Pd-Pd interaction gets down to control the growth process of Pd cluster as the cluster gets larger. It is hoped that our theoretical study would shed light on further designing high-performance TiO₂ supported Pd-based catalysts.