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.