Formation of Catalytic Active Sites in Hydrothermally Obtained Binary Ceria–Iron Oxides: Composition and Preparation Effects

Abstract

A series of mesoporous cerium−iron binary oxides was prepared by a hydrothermal technique using CTAB as a template. The influence of the Fe/Ce ratio and the variations in the preparation techniques such as the type of solvent and the precipitation agent, the approach of the template release, and the temperature of calcination on the phase composition, textural, structural, surface, and redox properties of the obtained materials was studied in details by XRD, nitrogen physisorption, TPR, FTIR, UV−vis, XPS, Raman, and Moessbauer spectroscopies. The materials were tested as catalysts in methanol decomposition and total oxidation of ethyl acetate. It was assumed that the binary materials represented a complex mixture of differently substituted ceria-and hematite-like phases. Critical assessment of their formation on the base of a common mechanism scheme was proposed. This scheme declares the key role of the formation of shared Ce−O−Fe structures by insertion of Fe 3+ in the ceria lattice and further competitive compensation of the lattice charge balance by the existing in the system ions, which could be controlled by the Fe/Ce ratio and the hydrothermal synthesis procedure used. This mechanism provides proper understanding and regulation of the catalytic behavior of cerium−iron oxide composites in methanol decomposition with a potential for hydrogen production and total oxidation of ethyl acetate as a model of VOCs.

Solvothermal Synthesis Routes to Substituted Cerium Dioxide Materials

“…The porosity of the particles was dependent on the volume of Ni(NO 3 ) 2 solution used in synthesis, and materials with~6.5 mol% Ni showed high catalytic performance in carbon monoxide oxidation. Mesoporous cerium-iron binary oxides prepared by a hydrothermal technique using CTAB as a template were tested as catalysts in methanol decomposition and total oxidation of ethyl acetate: low levels of Fe were dispersed in the fluorite structure, but higher levels gave clustering of Fe and ultimately phase separation above 50% Fe [75].…”

Multifunctional CeO2incorporated Fe2O3anchored on a rich porous structured carbon backbone for supercapacitors and adsorption of acid orange II

“…Raman peaks in the A 1g mode appear at 216 cm À1 , while Raman peaks in the E g mode appear at 286 and 398 cm À1 . 43 The peak at 658 cm À1 was ascribed to the disordered effect of Fe 2 O 3 . Additionally, the peaks of 1321 and 1581 cm À1 in the CFC diagram are the E g vibration modes corresponding to the sp 2 electronic structure of D and G modes.…”

Research Progress of a Composite Metal Oxide Catalyst for VOC Degradation

“…On this basis, Yang et al proposed a parallel series catalytic mechanism with more than two kinds of catalysts simultaneously. A series catalyst was constructed using a hollow structure MnO 2 (V O –MnO 2 ) with well-dispersed CuO as the shell and an oxygen-rich vacancy . The tight contact of the CuO/MnO 2 interface ensures the dynamic electron complement to maintain the continuity of the reaction.…”

“…A series catalyst was constructed using a hollow structure MnO 2 (V O −MnO 2 ) with well-dispersed CuO as the shell and an oxygen-rich vacancy. 33 The tight contact of the CuO/MnO 2 interface ensures the dynamic electron complement to maintain the continuity of the reaction. The sample energy band structure is shown in Figure 10 Perovskite oxide (general formula: ABO 3 ) has been widely used as an active component in the industrial catalytic oxidation of VOCs.…”

“…At present, many scholars have studied and discussed the factors influencing the activity of composite metal oxide catalysts . Tsoncheva et al prepared a series of mesoporous Ce–Fe binary oxides and tested the influence of the Fe/Ce ratio and different preparation techniques, such as the types of solvents and precipitators, different template release methods, and the composition and structure of the calcined temperature phase. Zhang et al synthesized a series of manganese copper bimetallic oxides (Mn x Cu y /AC) with different loads and studied the physical and chemical properties and catalytic performance of the samples .…”