Effect of Synthesis Conditions on Textural Characteristics of Mesoporous Cerium(IV) Oxide
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fect of Synthesis Conditions on Textural Characteristics of Mesoporous Cerium(IV) Oxide A. A. Maerlea, *, L. I. Rodionovaa, and I. F. Moskovskayaa aFaculty
of Chemistry, Moscow State University, Moscow 119991 Russia *e-mail: [email protected]
Received March 1, 2020; revised March 20, 2020; accepted April 10, 2020
Abstract—Mesoporous CeO2 has been prepared under hydrothermal conditions at 110–170°С in the presence of ionic and nonionic surfactants and characterized by SEM, low-temperature nitrogen adsorption– desorption, X-ray powder diffraction, and DTA–TG techniques. All synthesized samples had a specific surface area of up to 110 m2/g and a pore diameter of about 4 nm. It has been shown that the use of surfactants of various nature affects not only the final morphology of the oxide, but also its porous structure characteristics and chemical composition of its samples. It has been found that the use of ultrasound in the synthesis affects the specific surface area and average pore size of the samples. DOI: 10.1134/S096554412008006X
Cerium dioxide is an important functional material of considerable interest due to a set of special properties, such as chemical and thermal stability, redox lability (Ce4+/Ce3+), and a high oxygen storage capacity. It has found wide application as an electrolyte and an electrode in solid oxide fuel cells (SOFC); gas sensors as a UV blocker; and a catalyst for the oxidation of CO and various hydrocarbons, Fischer–Tropsch synthesis, photocatalytic oxidation, and neutralization of automobile exhausts [1–4]. It is known that the size and shape of crystals are determining factors in relation to many properties of materials based on CeO2 [5]. In particular, the catalytic activity of ceria depends on the specific surface area of the catalyst, and the specific surface area of the oxide can be increased by reducing the particle size or creating porosity. Thus, materials with a mesoporous structure, in which most of the pore space is accessible for reactants, are the most effective. That is why research aimed at selecting a synthesis method that results in a porous material with a high specific surface area and high thermal stability is especially important. The method of hydrothermal synthesis turned out to be a good alternative for producing ceria samples with controlled morphology and crystallite size [6–9]. One of the methods for producing CeO2 nanoparticles in the form of nanorods [10], nanocubes, or nanowires [11] is alkali treatment with cerium nitrate under hydrothermal conditions. However, the complete removal of sodium ions from the final synthesis product is very difficult, and their presence on the ceria surface adversely affects the reactivity of the material.
Another method aimed at optimizing the properties of the final material, such as high specific surface area, resistance to sintering of nanoparticles, and controllable particle growth, is the use of colloidal systems, surfactants, and polymers in the synthesis. When polymers (polyvinylpyrrolidone, polyvinyl alcohol)
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