Insights into Photocatalytic Selective Dehydrogenation of Ethanol over Au/Anatase–Rutile TiO2

Selective dehydrogenation of ethanol under mild conditions is of great significance for the conversion of ethanol into high-value chemicals. This work reports Au/anatase–rutile TiO2 photocatalysts for the targeted activation of O–H and α–H bonds and provides deep insights into the ethanol photocatalytic mechanism. In situ EPR, in situ FT-IR, and XPS were performed on Au/anatase–rutile TiO2 to explore the photocatalytic selective dehydrogenation process of ethanol. Under UV irradiation, O–H and α–H bonds of ethanol can be activated on TiO2 at the same time. Detailed investigations verified that Au/rutile TiO2 dominates the activation of O–H and facilitates the generated CH3CH2O• and CH3CH(OH)• diffused in the liquid phase for their subsequent reaction to 1,1-diethoxyethane (DEE). While radicals formed on Au/anatase TiO2 can not only react directly for DEE formation, they can also further dehydrogenate to acetaldehyde due to the strong adsorption on the surface of the catalyst and then produce DEE by condensation with ethanol. Au nanoparticles distributed at the anatase–rutile TiO2 interface show a significant electron–hole separation efficiency; therefore, the photocatalytic activity of ethanol selective dehydrogenation was improved. This study is of vital importance to the understanding of the reaction mechanism of photocatalytic ethanol conversion.