CO Oxidation Kinetics over Au/TiO2 and Au/Al2 O3 Catalysts: Evidence for a Common Water-Assisted Mechanism

Journal of the American Chemical Society
Johnny SaavedraBert D Chandler

Abstract

The mechanism of CO oxidation over supported gold catalysts has long been debated, with two prevailing mechanisms dominating the discussion: a water-assisted mechanism and a mechanism involving O-defect sites. In this study, we directly address this debate through a kinetic and mechanistic investigation of the role of water in CO oxidation over Au/TiO2 and Au/Al2O3 catalysts; the results clearly indicate a common water-assisted mechanism to be at work. Water adsorption isotherms were determined with infrared spectroscopy; the extracted equilibrium constant was essentially the same for both catalysts. Added water decreases CO adsorption on Au/TiO2, likely by blocking CO binding sites at the metal-support interface. Reaction kinetics (CO, O2, and H2O reaction orders) were essentially the same for both catalysts, as were measured O-H(D) kinetic isotope effects. These data indicate that the two catalysts operate by essentially the same mechanism under the conditions of these experiments (ambient temperature, significant amounts of water available). A reaction mechanism incorporating the kinetic and thermodynamic data and accounting for different CO and O2/COOH binding sites is proposed. The mechanism and kinetic data are treated wi...Continue Reading

Citations

Sep 29, 2020·Chemphyschem : a European Journal of Chemical Physics and Physical Chemistry·Si-Dun WangSheng-Gui He
Mar 26, 2021·Environmental Science and Pollution Research International·Chenglin FengMengkui Tian
Sep 20, 2018·Journal of the American Chemical Society·Todd WhittakerBert D Chandler
Jan 25, 2019·Journal of the American Chemical Society·Jian ZhangFeng-Shou Xiao
Feb 23, 2020·Journal of the American Chemical Society·K B Sravan KumarBert D Chandler
Jun 13, 2019·Inorganic Chemistry·Frederic C MeunierMichèle Besson
Sep 15, 2021·Chemical Communications : Chem Comm·Jingyi DingQingquan Lin
Sep 28, 2021·Chemical Society Reviews·David S PottsDavid W Flaherty
Dec 18, 2021·ACS Applied Materials & Interfaces·Pablo Jiménez-CalvoValérie Caps

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