Structure-activity Relation of Fe2O3–CeO2 Composite Catalysts in CO Oxidation

Abstract

A series of Fe 2 O 3 -CeO 2 composite catalysts were synthesized by coprecipitation and characterized by X-ray diffraction (XRD), BET surface area measurement, Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). Their catalytic activities in CO oxidation were also tested. The Fe 2 O 3 -CeO 2 composites with an Fe molar percentage below 0.3 form solid solutions with the CeO 2 cubic fluorite structure, in which the doped Fe 3+ initially substitutes Ce 4+ in fluorite cubic CeO 2 , but then mostly locate in the interstitial sites after a critical concentration of doped Fe 3+ . With an Fe molar percentage between 0.3 and 0.95, the Fe 2 O 3 -CeO 2 composites are mixed oxides of the cubic fluorite CeO 2 solid solution and the hematite Fe 2 O 3 . XPS results indicate that CeO 2 is enriched in the surface region of Fe 2 O 3 -CeO 2 composites. The Fe 2 O 3 -CeO 2 composites have much higher catalytic activities in CO oxidation than the individual pure CeO 2 and Fe 2 O 3 , and the Fe 0.1 Ce 0.9 composite shows the best catalytic performance. The structure-activity relation of the Fe 2 O 3 -CeO 2 composites in CO oxidation is discussed in terms of the formation of solid solution and surface oxygen vacancies. Our results demonstrate a proportional relation between the catalytic activity of cubic CeO 2 -like solid solutions and their density of oxygen vacancies, which directly proves the formation of oxygen vacancies as the key step in CO oxidation over oxide catalysts.

Synthesis, characterization and catalytic performance of ZnO–CeO2 nanoparticles in wet oxidation of wastewater containing chlorinated compounds

“…CeO 2 nanoparticles exhibited a strong peak at 462 cm -1 , corresponding to symmetric breathing mode (F 2g ) of oxygen in fluorite structure of CeO 2 (Jha et al 2016 Intensity (a.u.) which is in good correlation with the previous study (Bao et al 2008). ZnO exhibited the bands at 330 cm -1 (E 2 high-E 2 low), 437 cm -1 (E 2 high), and 658 cm -1 (E 2 low ?…”

Fe-doped ceria solids synthesized by the microemulsion method for CO oxidation reactions

“…In the case of CeO 2 , it has been widely demonstrated that its oxygen mobility abilities can be improved by the modification of its structure through the doping with different cations such as Zr [5], Zn [6], Eu [7], Cu [8], and Fe [9] among others. This enhancement of the oxygen mobility is directly related to the formation of oxygen vacancies, which has been reported as maximum for contents of doping agent around 10 atomic% in Ce-Eu [7], Ce-Fe [10,11] and Ce-Zn [6] systems. The promotion of oxygen vacancies in the modified ceria structures is especially attractive if these materials are employed as catalytic supports.…”

Synergy between gold and oxygen vacancies in gold supported on Zr-doped ceria catalysts for the CO oxidation

“…As presented in recent works, a correct evaluation of the evolution of oxygen vacancies population in pure and doped cerium oxides must be carried out by comparing the area ratio of the oxygen vacancies band and the F 2g signal (Ov/F 2g ) [8,42,43] in order to reduce the possible influence of the particle size and other effects over the shape and intensity of the signals [8,43,46,47]. The Figure 5 inset shows how the population of oxygen vacancies increases with the Zr At.% in our materials.…”