engleski

The comparison of advanced synthesis methods for ceria nanoparticles doped with manganese

Ceria (CeO2) is a material with many uses related to environmental protection and industry. Many of its applications depend on fluorite structure and easy shift between Ce3+ and Ce4+ oxidation states. During this interchange oxygen vacancies occur but thanks to its stable nature, the shift does not affect the cubic lattice. Some of the applications involving ceria are in catalysis, in solid oxide fuel cells and as a polishing material. Reducing dimensions to nanoscale is a good way to ensure greater specific surface area and catalytic activity. This makes the shift between Ce4+ and Ce3+ easier improving oxygen storage and mobility within the lattice. Another way of advancing ceria is doping. Ceria is mostly doped with transition metals. Most transition metals can enter the lattice thus enhancing catalytic activity and improving other properties while some don’t even enter the lattice. Manganese has many oxidation states and as such can improve oxygen storage and mobility and even thermal stability. There are many methods of synthesis for nanoparticles while advanced methods include hydrothermal, sol-gel and mechanochemical synthesis. Each of these methods has its advantages as well as problems such as harmful organic solvents, lack of temperature control or very small sample gain. In this work, our aim was to compare above mentioned methods of synthesis to prepare ceria as well as manganese doped ceria. The prepared samples were characterized by X-ray diffraction (XRD), infrared spectroscopy with Fourier transformation (FTIR) and N2 adsorption-desorption isotherms. Catalytic activity was tested on thermally treated samples at 500 °C for 2 hours. X-ray diffraction patterns were used to calculate ceria crystallite size via Scherrer equation. Each method of synthesis results with nanocrystalline ceria particles but in two of the used methods a minor phase appears beside CeO2. Smallest crystallite size was gained by the sol-gel synthesis. All samples show improved thermal stability with manganese incorporation.

Ceria ; Manganese ; Hydrothermal synthesis ; Sol-gel synthesis ; Mechanochemical synthesis

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