New insights on the electronic factor of the SMSI effect in Pd/TiO2 nanoparticles

Whereas observed and explored for over 40 years, there are still open questions regarding the nature of the Strong Metal-Support Interaction (SMSI) effect. The lack of a precise determination of the atomic mechanisms of electronic and geometrical factors of the SMSI effect hinders the application of metal-support systems towards several catalytic reactions. The present study sheds light on the electronic factor of the SMSI effect in Pd/TiO2 nanoparticles by using Near Ambient Pressure Photoelectron Spectroscopy (NAP-XPS), Ultraviolet Photoelectron Spectroscopy (UPS), and Density Functional Theory (DFT) calculations. The electronic and geometrical factor of the SMSI effect were observed during reduction treatment at 300 °C and 500 °C, respectively. The results enable mapping the electronic factor during reduction treatment at 300 °C, where a charge transfer from Pd nanoparticles to TiO2 support through Pd-O-Ti entities existing at the Pd-TiO2 interface is observed. Furthermore, the charge transfer is mediated by O p states present at the Pd-TiO2 interface.