Theoretical investigation on oxygen source for selective oxidation of glycerol at Au/CeO2−x and Pt/CeO2−x interfaces

Abstract

Glycerol is considered as a significant green platform chemical, and many efforts have been devoted to design and prepare the efficient catalysts to convert glycerol to glyceric acid; however, the active site as well as reaction mechanism of glycerol oxidation remains rather ambiguous in terms of different oxygen sources. Herein, we studied the oxidation reaction of glycerol to glyceric acid over the catalytic systems of Au/CeO2−x and Pt/CeO2−x on periodic density functional theory (DFT) calculation in detail. By the optimization of catalyst structure models and comparison of substrate adsorption configurations, the interfacial sites of supported catalysts (Au/CeO2−x and Pt/CeO2−x) are regarded as the intrinsic active sites. Potential energy curve confirms that the reaction mechanism of glycerol oxidation includes two main pathways: OH− and O2 as oxygen sources in base and base-free environment, respectively. Mechanism studies indicate that Au/CeO2−x interface facilitates the dehydrogenation of C−H/O−H bond, which further promotes the formation of glyceraldehyde. Moreover, Pt/CeO2−x is favorable for the transfer of intramolecular H, resulting in excellent catalytic performance for the oxidation of glyceraldehyde to glyceric acid. The O2− was involved in oxidative dehydrogenation as active oxygen in base-free condition, and Pt/CeO2−x was more favorable for base-free glycerol oxidation. This work offers detailed insights into interfacial synergy effects of supported catalytic systems and the reaction mechanism of glycerol oxidation, which will pave the way for the selection of solvent conditions toward selective oxidation reaction.