Early-Stage Deactivation of Platinum-Loaded TiO2 Using In Situ Photodeposition during Photocatalytic Hydrogen Evolution

This work unravels a sudden deactivation of Pt/TiO2 (P25) during the initial stages of photocatalytic H2 evolution from aqueous solution that, until now, has gone unnoticed, using a unique combination of in situ photodeposition of Pt with an on-line gas detector system. Utilizing a set of techniques, including highresolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), UV-visible diffuse reflectance spectroscopy (DRS-UV-vis), X-ray powder diffraction (XRD), Raman spectroscopy, and physisorption, we were able to attribute this deactivation to a shift in mechanism, accompanied by an increase in CO concentration. Key to this phenomenon is the ratio of Pt atoms to oxygen vacancies, which were created through ultrasonic pretreatment and in situ UV irradiation in the bulk and surface, respectively. We also observed a potential additional contribution to the deactivation by encapsulation of the Pt nanoparticles, indicating that strong metal−support interaction (SMSI) may indeed happen in aqueous and ambient conditions. Furthermore, we encourage implementing the concept of a “dynamic” catalyst to photochemistry that opens up a new approach toward understanding the complex mechanisms and kinetics in heterogeneous photocatalysis.