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

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.