Mechanisms and Energetics of Complete Ethylene Oxidation on a PdAu Bimetallic Catalyst from a Theoretical Perspective

: The complete catalytic oxidation of ethylene at low temperatures is of great significance for the preservation of agricultural products during transportation. Au-based catalysts with various Pd ensembles have recently shown promise in catalytic oxidation. In this work, the catalytic mechanisms and energetics for ethylene oxidation on a PdAu bimetallic catalyst with a second neighboring Pd configuration were systematically investigated from a theoretical perspective. It is found that the PdAu bimetallic catalyst can produce seven adsorption sites for ethylene oxidation. The entire reaction network consists of four processes: C-O bond formation, C-C bond cleavage, CO2 formation, and H2O formation, which involve a total of 21 adsorbed species and 35 elementary reactions. Among the several possible oxygenates, CH2CO is an important intermediate and has the lowest energy barrier of the C-C bond cleavage. The second neighboring Pd configuration makes O active in C-O bond formation. Finally, the most energetically favorable pathway of complete ethylene oxidation was determined as CH2CH2 -> CH2CH2O(OME) -> CH2CHO -> CH2CO -> CH2 -> CH -> CHO -> CO -> CO2. In all, the PdAu bimetallic catalyst shows high activity for the complete oxidation of ethylene. We hope that this comprehensive work can provide a deeper understanding of the hydrocarbon oxidation on bimetallic catalysts.