Preferential Growth of Pt on Rutile TiO2

The characterization of Pt/TiO2 (Degussa P25) catalyst system using atomic resolution Z-contrast images and electron energy loss spectroscopy in the scanning transmission electron microscope has recently revealed that Pt particles have a strong tendency to nucleate on the rutile phase of TiO2 rather than anatase. Comparative ab initio pseudopotential calculations for Pt and Pt_2 on the stoichiometric and reduced TiO2 surfaces, and oxygen vacancy (V_O) formation energies are performed to address the microscopic origin of this finding. The results, which show that Pt actually binds more strongly to anatase surfaces, indicate that the selective growth of Pt on rutile must be controlled by the lower formation energy of V_O on rutile, and possibly by the stronger tendency of V_O sites on rutile to trap large Pt clusters compared to anatase.