Web Release Date: January 12,
Origin of High Activity and Selectivity of PdAu(001) Bimetallic Surfaces toward Vinyl Acetate Synthesis
and
Department of Physics and Astronomy, University of California, Irvine, California 92697-4575, ICTS, Chinese Academy of Sciences, Beijing, 100080, China, and Surface Science Laboratory and Department of Physics, Fudan University, Shanghai-200433, China
Received: August 27, 2007
In Final Form: October 31, 2007
Abstract:
We perform systematic density functional studies to elucidate the mechanism of vinyl acetate (VA) synthesis
on Pd/Au(001). Atomic geometries, activation energies, and reaction energies are determined for three separate
reaction stages: coupling of ethylene and acetate; 
-H elimination; and VA desorption. Significantly, we
find that the Pd "monomer" pair is much more robust in all three reaction stages than large Pd ensembles
such as Pd monolayers, mainly due to high mobility of reactants on surrounding Au sites. The remarkably
high activity and selectivity of VA reaction on PdAu bimetallic surfaces observed by Goodman et al. are
exclusively attributed to the ensemble effects.
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