A series of multifunctional catalysts of three-dimensionally ordered macroporous (3DOM) ZrO2-supported core–shell structural Au@CeO2−δ nanoparticles were successfully synthesized by the one-pot method of gas bubbling-assisted membrane reduction–precipitation (GBMR/P). All the catalysts possess a well-defined 3DOM structure with interconnected networks of spherical voids, and the Au@CeO2−δ core–shell nanoparticles with different molar ratios of Au/Ce are well dispersed and supported on the inner wall of the uniform macropore. 3DOM support facilitates the contact efficiency between solid reactant and catalyst, and the Au@CeO2−δ core–shell nanoparticles with strong metal-oxides interaction improve the amount of active oxygen species and the sintering resistance of supported Au nanoparticles due to the optimization of the interface area by formation of the metal-oxides core–shell (MOCS) nanostructure particles. 3DOM Au@CeO2−δ/ZrO2 catalysts exhibit high catalytic activity and stability for diesel soot oxidation. Among the as-prepared catalysts, 3DOM Au@CeO2−δ/ZrO2-2 catalyst with the moderate thickness of CeO2−δ nanolayer shell shows the highest catalytic activity for soot combustion, i.e., its T50 is 364 °C. In summary, 3DOM Au@CeO2−δ/ZrO2 catalysts are excellent systems for catalytic combustion of solid particles or macromolecules, and the design concept and facile synthesis method of 3DOM oxide-supported MOCS nanoparticle catalysts can be extended to other metal/oxide compositions.
Soot particles in diesel engine exhaust is one of the main reasons for hazy weather and elimination of them is urgent for environmental protection. At present, it is still a challenge to develop new catalysts with high efficiency and low cost. In this paper, a kind of K modified three-dimensionally ordered macroporous (3DOM) MnCeOx/Ti0.7Si0.3O2 catalysts are designed and synthesized by a sample method. Due to the macroporous structure and synergistic effect of K, Mn, and Ce, the KnMnCeOx/Ti0.7Si0.3O2 (KnMnCeOx/M-TSO) catalysts exhibit good catalytic performance for soot combustion. The catalytic activity of K0.5MnCeOx/M-TSO was the best, and the T10, T50, and T90 are 287, 336, and 367 °C, respectively. After the prepared catalyst was doped with K, the physicochemical properties and catalytic performance changed significantly. In addition, the K0.5MnCeOx/M-TSO catalyst also somewhat exhibits sulfur tolerance owing to it containing Ti. Because of its simple synthesis, high activity, and low cost, the prepared KnMnCeOx/M-TSO catalysts are regarded as a promising candidate for application.
A new type of electronic effect, polarized metal-support interaction (pEMSI), in oxide-supported Pd nanoparticles describing the enhanced accumulation of electrons at the superficial surface is responsible for improved catalytic H2 evolution.
A series of alkali metals and cerium-modified La–Co-based perovskite catalysts were successfully prepared by a simple method using glucose as a complexing agent. The physicochemical properties of catalysts were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption, H2-temperature-programmed reduction (TPR), O2-temperature-programmed desorption (TPD), soot-TPR, NO-temperature-programmed oxidation (TPO), X-ray photoelectron spectroscopy (XPS), etc. Among the catalysts, La0.9Ce0.05K0.05CoO3 possesses the highest catalytic activity for soot combustion, with T10, T50, and T90 values of 269, 309, and 342 °C, respectively. In the presence of 10% H2O, T90 is significantly reduced to 327 °C. As far as we know, the catalytic performance of the La0.9Ce0.05K0.05CoO3 perovskite oxide catalyst is one of the best results in current reports for soot combustion, especially for T50 and T90. The substitution of A sites by K and Ce ions produces numerous active sites of Co2+–Ov on the surface of the La0.9Ce0.05K0.05CoO3 catalyst and enhances the oxygen storage capacity by redox recycling between Ce4+ and Ce3+. The La0.9Ce0.05K0.05CoO3 catalyst also possesses a stronger ability of NO adsorption, storage, and NO-to-NO2 oxidation compared to other prepared catalysts. Based on the results of in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and density functional theory (DFT) calculations, Langmuir–Hinshelwood (L–H) and Mars–van-Krevele (MVK) mechanisms were proposed as the main reaction mechanisms for soot combustion. More importantly, the La0.9Ce0.05K0.05CoO3 catalyst exhibits good resistance ability for sulfur and water. These results provide a promising strategy for designing and preparing highly efficient and low-cost catalysts for the practical application of soot particle removal.
The recent advances in the preparation of Mn-based oxide catalysts with special morphologies and their catalytic performance for the removal of air pollutants are summarized.
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