Insights into support effects on Ce-Zr-O mixed oxide-supported gold catalysts in CO oxidation

Abstract

Au/Ce1–xZrxO2 catalysts (x = 0–0.8) were prepared by a deposition-precipitation method using Ce1–xZrxO2 nanoparticles as supports with variable Ce and Zr contents. Their structures were characterized by complimentary means such as X-ray diffraction, Raman, scanning transmission electron microscopy and X-ray photoelectron spectroscopy (XPS). These Au catalysts possessed similar sizes and crystalline phases of Ce1–xZrxO2 supports as well as similar sizes and oxidation states of Au nanoparticles. The oxidation state of Au nanoparticles was dominated by Au0 especially in CO oxidation. Their activities were examined in CO oxidation at different temperatures in the range of 303–333 K. The CO oxidation rates normalized per Au atoms increased with the increasing Ce contents, and reached the maximum value over Au/CeO2. Such change was in parallel with the change in the oxygen storage capacity values, i.e. the amounts of active oxygen species on Au/Ce1–xZrxO2 catalysts. The excellent correlation between the two properties of the catalysts suggests that the intrinsic support effects on the CO oxidation rates is related to the effects on the adsorption and activation of O2 on Au/Ce1–xZrxO2 catalysts. Such understanding on the support effects may be useful for designing more active Au catalysts, for example, by tuning the redox properties of oxide supports.