Preferential Growth of Pt on Rutile TiO2

TL;DR

This study investigates why platinum preferentially grows on rutile TiO2 surfaces despite stronger binding to anatase, revealing that oxygen vacancy formation energies influence nucleation sites.

Contribution

The paper combines experimental imaging with ab initio calculations to explain the microscopic origin of Pt's preferential growth on rutile TiO2.

Findings

Pt binds more strongly to anatase surfaces.

Oxygen vacancy formation energy is lower on rutile.

V_O sites on rutile trap larger Pt clusters.

Abstract

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.