engleski

Mechanochemical synthesis of manganese doped ceria nanoparticles

Ceria, CeO2, is an important rare earth oxide material with cubic fluorite type structure. Pure ceria is an n-type semiconductor with two stabile oxidation states, Ce3+ and Ce4+, making it suitable for various applications. [1] Energy and catalyst applications are mostly based on great oxygen storage capacity, redox properties and ionic conductivity of ceria. Ceria is frequently used in solid oxide fuel cells, catalysis, sensors and high temperature ceramics. [2] Good catalytic properties and ionic conductivity depend on thermal stability which nanomaterials lack. Doping with various metals, including transition metals such as manganese helps to overcome pure ceria shortcomings. Manganese is known to have many oxidation states and because of the synergistic effect between MnOx and CeO2 can modify oxygen storage capacity and mobility. Mechanochemical synthesis is a method that can yield fine homogenous powders. Intensive mechanical milling causes chemical reactions between precursors and results with products that usually form at much higher than room temperatures. Negative features of ball milling can be agglomeration or heat generated while milling. Nanoparticles of pure and Mn doped ceria were attained by mechanochemical synthesis from chlorides. After synthesis, x-ray diffraction (XRD) and differential thermal analysis (DTA) were performed giving insight into acquired phases and their thermal decomposition. Scherrer equation was used on 500°C for 2h annealed samples to calculate ceria crystallite size. Morphology of the prepared samples was investigated on a scanning electron microscope (SEM), while N2 adsorption-desorption isotherms gave insight into surface and pore features. Catalytic character of doped and pure ceria samples was measured via toluene conversion in a 150°C – 450°C temperature interval. All of the prepared samples show pure ceria phase after thermal treatment. DTA and XRD results show that the incorporation of manganese in ceria enables easier ceria formation as well as generates smaller crystallites.

Ceria ; Manganese ; Mechanochemical synthesis

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