SBA-15-supported gold nanoparticles decorated by CeO 2: Structural characteristics and CO oxidation activity

Abstract

The influence of SBA-15 substrate modified with CeO 2 on the catalytic response of supported gold catalysts in the CO oxidation reaction was investigated. The mesoporous CeO 2/SBA-15 materials (5, 10, 15 and 20 wt% of CeO 2) were prepared by incipient wetness impregnation of synthesized SBA-15 substrate whereas the supported gold catalysts were prepared by deposition–precipitation method. The dried Au/SBA-15 and Au/CeO 2/SBA-15 catalysts were characterized by elemental analysis (EDX), N 2 adsorption–desorption isotherms, X-ray diffraction (XRD), UV–vis diffuse reflectance spectroscopy (UV–vis DRS), high resolution transmission electronic microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) and their catalytic activity was investigated by the temperature-programmed CO oxidation reaction performed in temperature range 26–205 °C. Catalytic activity was found to increase with the CeO 2 loading even though this increase was not linear: the highest catalytic activity was observed for the catalyst loaded with 10 wt% CeO 2. This result was explained in terms of the combined effects of the higher stability of gold particles on the support. It was found that the Au nanoparticles in the CeO 2/SBA-15 substrates could be stabilized more efficiently than those on Ce-free SBA-15 material. For the Ce-containing catalysts, a superior performance of the Au/10%CeO x /SBA-15 catalyst was related to multiple factors such as (i) highest dispersion of Au species on the support surface (by XPS and HRTEM), (ii) highest surface exposure of the Au δ+ species (by XPS), and (iii) probably a synergetic effect between the gold nanoparticles and the CeO 2 nanoparticle size (by XRD, UV–vis and HRTEM).