Exploring the properties of Ag5–TiO2 interfaces: stable surface polaron formation, UV-Vis optical response, and CO2 photoactivation

Abstract

Using a combination of first-principles modelling, X-ray absorption spectroscopy, and diffuse reflectance spectroscopy measurements, we explore the properties of Ag₅-modified TiO₂ surfaces. A general electron polarization phenomenon associated with surface polarons on TiO₂ has been revealed theoretically and confirmed experimentally. First, the Ag₅ cluster donates an electron to TiO₂, leading to the formation of polaronic Ti³⁺ 3d¹ states on the rutile TiO₂(110) surface. The analysis of polarization effects in the nearby electronic structure accompanying the polaron formation is confirmed with X-ray absorption spectroscopy measurements at the Ti K-edge of TiO₂ nanoparticles. Next, the UV-Vis optical absorption spectrum of the polaronic state is also computationally modelled and an enlargement of the polaron wavefunction is predicted. Moreover, we find an overall improvement of the UV-Vis optical response of the material through diffuse reflectance spectroscopy measurements. Finally, we predict that charge-transfer processes at the Ag₅–TiO₂ interface triggered by solar photons might allow for a photoinduced activation of CO₂ by sunlight.