Ensemble effects on ethylene dehydrogenation on PdAu(001) surfaces investigated with first-principles calculations and nudged-elastic-band simulations

The ensemble effects on adsorption and dehydrogenation of ethylene on PdAu(001) bimetallic surfaces are systematically investigated through first-principles calculations and nudged-elastic-band simulations. Significantly, we find that ethylene dehydrogenation is inhabited under ambient reaction temperature on the most popular second-neighbor Pd ensembles, because of the insufficient attraction of Au and Pd-Au bridge sites toward vinyl and the eliminated hydrogen in the transition state. This finding is essential for understanding the mechanism of complex reactions on such bimetallic catalysts and the synthesis of vinyl acetate. Linear correlations are found among the activation energies, reaction energies, and adsorption energies, but no obvious relationship exists between the surface activity and the Pd0.2em0exd-band center.