Oxygen sensing with mesoporous ceria–zirconia solid solutions

Effect of preparation procedure on the formation of nanostructured ceria–zirconia mixed oxide catalysts for ethyl acetate oxidation: Homogeneous precipitation with urea vs template-assisted hydrothermal synthesis

“…Indeed, the profile fitting of the XRD reflections using Topas 4.2 program clearly show that for all bi-component materials they are superposition of reflections characteristic of cubic Fm-g3m and tetragonal P4 2 /nmc phases in different ratio depending on the composition and the preparation procedure used. The observed results are in contrast with the data reported in [3,37,48], where the segregation of a second phase was reported only for the samples with relatively high Zr content and confirm the conclusion reported by Zhang et al [49] that the phase segregation depends on the nanoparticle size. Formation of metastable tetragonal phase for the Ce x Zr 1 − x O 2 samples when x varied between 0.35 and 0.65 was also reported in [8,18].…”

“…However, further increase in Zr/Ce ratio (3Ce7Zr U) provokes slight shifting and broadening of the main Raman-active mode accompanied with a decrease in its intensity. This could be assigned to partial replacement of Ce ions with Zr ones, resulting in M O bonds shortening [37] and formation of smaller crystallites with defect structure. The appearance of additional bands at 140, 269 and 307 cm −1 evidences the crystallization of second tetragonal phase with P4 2 /nmc space group.…”

“…Transition of cubic to tetragonal fluorite phase occurs with increasing the zirconium content [35] and the degree of distortion of the cubic fluorite structure strongly depends on the synthesis method, particle size and thermal treatment [36]. Several methods, such as precipitation, microemulsion, microwave, hydrothermal synthesis including also supercritical water, flame spray, sol-gel, high temperature solid state reaction, high energy ball milling, and combustion synthesis have been applied to synthesize mixed oxide CeO 2 -ZrO 2 materials [ [8,16,30,[37][38][39][40] and Refs. therein].…”

“…Template-assisted hydrothermal synthesis is also a promising approach for preparation of nanostructured metal oxide materials with high surface area and well developed mesoporous structure. Typically, the crucial point in this synthesis pathway plays the nature of template used and some results on the application of solid ordered mesoporous silicas as "hard" templates [37] or large organic molecules such as CTAB, Brij56 and Pluronic 123 as "soft" templates [44,45] are used for preparation of CeO 2 -ZrO 2 mixed oxides. In the case of "soft" templated approach a negligible effect of the surfactant nature on the crystallization of solid solution is established in [45].…”

Noble Metal-Free Ceria-Zirconia Solid Solutions Templated by Tobacco Materials for Catalytic Oxidation of CO

“…CeO 2 -ZrO 2 mixed compound, which act as an oxygen storage component to maintain the air to fuel ratio close to stoichiometric is present in the washcoat deposited on either a ceramic or metallic monolith [7,8]. A number of methods have been developed for the syntheses of Ce 1−x Zr x O 2 solid solution including solid-state synthesis [9], high-energy milling [10], hydro/solvothermal synthesis [11,12], co-precipitation [13,14], the citrate method [15], inverse micelles [16], and template method [17]. Ce 1−x Zr x O 2 solid solutions prepared by different methods showed different activities for CO oxidation [18,19].…”