Abstract
It is demonstrated that the synthesis procedure for preparing three-dimensionally ordered macroporous (3DOM) Pr-doped ceria catalysts using a polymethylmethacrylate (PMMA) template not only affects the porous structure, but also the chemistry of the ceria surface. The PMMA template does not affect the crystalline features (type of phases, crystallite size, and cell parameter) of Pr-doped ceria, Ce and Pr location into the particles, and the bulk reduction of the Ce-Pr mixed oxide catalysts. On the contrary, the utilization of the PMMA template improves both the porosity and surface redox properties. 3DOM Ce-Pr mixed oxide catalysts combine micro, meso, and macropores, the most area being in the macropore range, while a reference unshaped catalyst presents poor porosity in all ranges. However, the catalyzed CO oxidation rates do not correlate with the surface area of the catalysts (neither micro nor meso/macro). The Ce-Pr-3DOM catalyst also presents improved surface reducibility with regards to the counterpart reference material prepared without the template, and improved redox behavior under reaction conditions; that is, it has a higher area and this area is reduced and reoxidized more easily. X-ray photoelectron spectroscopy analysis evidences that this is mainly attributed to praseodymium cations, which accomplish redox cycles more easily than cerium cations.
Highlights
Three-dimensionally ordered macroporous (3DOM) solids have been successfully developed in the last few years for a number of catalytic applications
From the bulk to surface and vice-versa, surface species, The goal of the current study is to demonstrate that the synthesis procedure followed to obtain and so on [11,12]
It can be concluded that according to the Raman spectroscopy, XRD, and helium density results, the utilization of the PMMA template does not affect the crystalline features of the catalysts, which seem to be related to the chemistry and thermal history of the synthesis process
Summary
Three-dimensionally ordered macroporous (3DOM) solids have been successfully developed in the last few years for a number of catalytic applications. Ceria-based 3DOM catalysts have demonstrated improved diesel soot combustion activity with regards to disordered counterparts, and this improvement has been attributed to the enhanced solid-solid contact between the soot and catalyst particles [1,2,3,4,5]. Au/3DOM-CeO2 has shown better catalytic performance for formaldehyde oxidation than similar unshaped catalysts, and this improvement was attributed to the good Au dispersion and higher Au loading content [8]. All these examples evidence that the macroporous structure of 3DOM solids benefits the catalytic performance due to improvements related to this particular morphology, but little is known about. Ji et al [9] suggested that the improved catalytic activity of Co‐ and Fe‐
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