Constructing a high concentration CuO/CeO2 interface for complete oxidation of toluene: The fantastic application of spatial confinement strategy

In this paper, CeO2 substrate was prepared by the sol-gel method, further CuO was introduced by adding the copper complexes with chelating agents into the sol-gel precursors of CeO2, in which different chelating agents (β-cyclodextrin, glucose and trimesic acid) were tried. This synthesis method helps the CuO species to disperse very uniformly in the CeO2 substrates. When the amount of copper oxide is up to 33 mol%, the CuO/CeO2 samples can still maintain a highly dispersed state. The CeO2 and CuO/CeO2 samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction of hydrogen (H2-TPR), temperature-programed desorption (O2-TPD), etc. It is found that the CuO/CeO2 catalyst prepared by β-cyclodextrin (βCuO/CeO2) exhibits better catalytic performance owing to the higher dispersion, higher specific surface area, more defects, more active Ce3+ and Cu+ ions, more oxygen vacancies, more surface active oxygen, relatively better low temperature reducibility, and the exposed (110) active facets. In the condition of 1000 × 10−6 toluene in air and WHSV = 60000 mL/(g·h), the T90 for toluene conversion is 227 °C. The reaction mechanism of toluene catalytic oxidation over CeO2 and βCuO/CeO2 is discussed by the study of in-situ DRIFTs. This work affords a simple and efficient method for the synthesis of highly dispersed bimetal oxide catalysts with high contents.