Pretreatment Effect on Ceria‐Supported Gold Nanocatalysts for CO Oxidation: Importance of the Gold–Ceria Interaction

E-ISSN： 2194-4296|6|2|379-390

ISSN： 2194-4288

Source： ENERGY TECHNOLOGY (ELECTRONIC), Vol.6, Iss.2, 2018-02, pp. : 379-390

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Abstract

AbstractThe encapsulated Au/CeO₂ hollow composite shows the effects of different pretreatment conditions on CO oxidation, showing complete conversion temperatures for CO in the order O₂ pretreatment (T₁₀₀=74 °C)>N₂ pretreatment (T₁₀₀=142 °C)>CO pretreatment (T₁₀₀=167 °C). Because of the good confinement provided by the uniform pores of as‐prepared CeO₂, the size of deposited Au nanoparticles embedded in the pores of CeO₂ can be well controlled. Pretreated Au/CeO₂ catalysts have a good stability with no clear deactivation even after 70 h. A systematic characterization was performed by employing various techniques (XRD, H₂ temperature‐programmed reduction, scanning transmission electron microscopy with energy‐dispersive spectroscopy, Raman spectroscopy, X‐ray photoelectron spectroscopy, and in situ diffuse reflectance infrared Fourier transform spectroscopy) to understand the importance of the Au–CeO₂ interaction. This revealed that the O₂ pretreatment may result in (a) the migration of lattice oxygen atoms to the surface region and clearly increased number of oxygen vacancies in CeO₂; (b) the increase of Au−O_x and Au−O_x−Ce bond lengths; (c) the creation of electron holes in the CeO₂ substrate and electron deficiencies in Au nanoparticles as well as a strong Au–CeO₂ interaction; and (d) increased number of bicarbonates on the surface and Au^δ+−CO bonds were produced during CO oxidation. All these features are responsible for an overall enhanced activity of CO oxidation and high durability of the Au/CeO₂ hollow composite.