In this work, a core–shell
structured
CeO2@Co3O4 catalyst was successfully
prepared by using a zeolitic imidazolate framework-based material
as a sacrificial template. The structure, morphology, and physicochemical
characteristics of these materials were investigated by X-ray diffraction,
N2 sorption, Fourier transform infrared spectroscopy, Raman
spectroscopy, field emission scanning electron microscopy, transmission
electron microscopy, X-ray photoelectron spectroscopy, temperature-programmed
desorption, and temperature-programmed reduction studies. Compared
with pure Co3O4 and CeO2, the CeO2@Co3O4 sample displayed superior catalytic
performance (T
90 = 225 °C) toward
toluene oxidation. Results demonstrated that the CeO2@Co3O4 sample exhibited a core–shell structure,
with hierarchically wrinkled surfaces. This unique structure, especially
the interface between the core and the shell, endowed the CeO2@Co3O4 catalyst with better activity.
In addition, there was a synergistic effect between cerium and cobalt
oxides in the core–shell bimetallic sample, which was responsible
for the improved performance of the material. Moreover, surface-active
oxygen species involved and played a significant role in toluene oxidation.
Nowadays, the oxidation activity at the low-temperature regime for Co3O4 catalysts needs to be improved to meet the stringent regulation of multi-pollutant diesel exhaust. Herein, nanoflower-like Co3O4 diesel oxide catalysts (DOCs) were fabricated with the addition of a low-content Pt to trigger better catalytic activities for oxidizing multi-pollutants (CO, C3H6, and NO) emissions by taking advantage of the strong-metal supporting interaction. Compared to the conventional DOCs based on Pt/Al2O3, the as-synthesized Pt/Co3O4 catalysts not only exhibited better multi-pollutants oxidation activities at the low temperature but also obtained better resistance toward NO inhibition. Moreover, Pt/Co3O4 catalysts showed exceptional hydrothermal durability throughout long-term tests in the presence of water vapor. According to the XPS and H2-TPR results, Pt promoted low-temperature catalytic activity by increasing the active surface oxygen species and reducibility due to the robust synergistic interaction between metallic Pt and supporting Co3O4. Meanwhile, TGA curves confirmed the Pt atoms that facilitated the desorption of surface-active oxygen and hydroxyl radicals in a low-temperature regime. Furthermore, instead of probing the intermediates during CO and C3H6 oxidation for Pt/Co3O4 catalysts, which included carbonates, formate, and acetate species, in situ DRIFTs experiments also revealed C3H6 oxidation mainly took place over metallic Pt sites.
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