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Volume 91 Issue 6 | p. 31 | Concentrates
Issue Date: February 11, 2013

CO Serves As Its Own Cocatalyst On Gold

The presence of neighboring CO molecules on gold nanoclusters enhances dioxygen oxidation of CO to carbon dioxide
Department: Science & Technology
News Channels: JACS In C&EN, Nano SCENE
Keywords: gold catalysis, CO oxidation, gold clusters, gold nanoparticles
This quantum molecular dynamics simulation shows that on small gold clusters the intermediate formed by reaction of CO with O2 readily forms CO2 after an attack by a neighboring CO molecule.
Credit: Xiao Cheng Zeng/U of Nebraska
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Molecular dynamics studies show that CO serves as a cocatalyst in self-oxidation reactions on gold clusters (yellow) by enhancing the rate of O–O (red) bond scission in an intermediate structure (center) to form CO2.
Credit: Xiao Cheng Zeng/U. Nebraska
Three pyramidal structures made out of gold balls. One dioxygen molecule and two CO molecules are bound in the left two structures. They are replaced in the third by two escaping carbon dioxide molecules.
 
Molecular dynamics studies show that CO serves as a cocatalyst in self-oxidation reactions on gold clusters (yellow) by enhancing the rate of O–O (red) bond scission in an intermediate structure (center) to form CO2.
Credit: Xiao Cheng Zeng/U. Nebraska

Since the unexpected finding more than 20 years ago that gold, an archetypal inert metal, can serve as a carbon monoxide oxidation catalyst, scientists have searched for the basis of the precious metal’s reactivity. Chemists now know that nanosized gold clusters can catalyze various oxidations, esterifications, and epoxidations, and they have uncovered a few of the mechanistic details. A computational study has found that CO can surprisingly provide a cocatalytic assist to gold nanoclusters during oxidation reactions. This self-oxidation mechanism—uncovered by Xiao Cheng Zeng of the University of Nebraska, Lincoln; Yong Pei of Xiangtan University, in China; and coworkers—reveals a new twist to how gold functions as a catalyst (J. Am. Chem. Soc., DOI: 10.1021/ja309460v). The researchers found that when CO is bound to certain triangular Au3 active sites on gold nanoclusters in the presence of O2, the CO molecule helps facilitate bond scission in an adjacent OCOO intermediate. The analysis shows that an attack on the intermediate by the Au3-bound CO neighbor would significantly accelerate the rate of O–O bond breaking, resulting in formation of two CO2 molecules.

 
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