Distribution of oxygen vacancies and their impact on the charge state of Pt on TiO2

Abstract

It is well known that interactions between the support and metal particles, called metal–support interactions, considerably affect the activity of supported metal catalysts. Two representative consequences of these interactions are the formation of lattice defects at the metal–support perimeter and the change in the charge state of metal particles. However, the identification of control parameters for tuning metal–support interactions is not simple because many factors can affect metal–support interactions. Herein, a model Pt/TiO₂ catalyst based on an epitaxial TiO₂ thin film was developed and the distribution of oxygen defects and the charge state of Pt on this catalyst were investigated using scanning transmission electron microscopy, electron energy loss spectroscopy, X-ray photoelectron spectroscopy, and first-principles calculations. Results showed that oxygen vacancies are easily formed just below Pt nanoparticles. Moreover, it was revealed that Pt nanoparticles supported on TiO₂ (101) are negatively charged. Oxygen vacancies promote charge transfer to Pt nanoparticles, and Pt becomes more negatively charged than that on stoichiometric TiO₂. This study demonstrates that the charge state of Pt is affected by the presence of oxygen vacancies on the support, providing an important guideline for controlling metal–support interactions to develop catalysts with desired properties.