Evidencing active-site transfer in the hetero-structure photo-catalytic processes via NMR molecular probes

Abstract

Recently metal-support interaction (MSI) has attracted considerable attention in photocatalysis. Some studies emphasize the importance of active sites on photocatalysts; however, there are no reports on site changes under MSI in real reactive conditions. Herein, an operando nuclear magnetic resonance technique was proposed to study such site changes on anatase TiO2 and Pt/TiO2, through a gas-probe method, in CH3OH reforming. The photocatalytic oxidation efficiency of CH3OH by pure TiO2 decreased immensely under extra-gas conditions, while that by Pt/TiO2 was unaffected. The surface of pure TiO2 were occupied by injected gas molecules, making CH3OH inaccessible to active sites. However, in Pt/TiO2, CH3OH adsorption sites changed from TiO2 surface to metal-Pt/TiO2 interface as confirmed by H2 gas-probe experiments. This study provides a deeper understanding of active sites transfer by MSI and leverages the gas-probe method for its detection to guide the development of technology to test active-site positions in heterogeneous catalysts.