engleski

Hydrothermally derived doped ceria nanocatalyst

Cerium dioxide or ceria (CeO2) is a rare earth metal oxide of great importance with numerous applications in industry, energetics and environmental protection. Catalytic oxidation of volatile organic compounds (VOCs) has been a burning issue over the last couple of years and ceria has been considered a useful catalyst for this process, especially in the nanosized form due to the increased specific surface area. The advantages of ceria are reversible oxygen storage and release capacity, resistance to poisoning and low cost, but the possible problems are poor low-temperature catalytic activity and thermal stability. For this reason, various transition metals, such as Mn, Fe, Co, etc., are doped into the ceria crystal lattice to improve its properties. In this work, pure and doped ceria nanocatalysts have been obtained through a simple, affordable and environmentally friendly method - the hydrothermal synthesis, which involves metal salts in sodium hydroxide solution under high pressure and temperature. In the doped samples, 10 mol % of cerium was replaced with Mn, Fe, Co, Ni, Cu and Zn ions. The prepared samples were characterized in detail using X-ray diffraction (XRD), transmission electron microscope (TEM), energy dispersive X-ray spectroscopy (EDX), Fourier-transformed infrared spectroscopy (FTIR) and adsorption-desorption N2 isotherms, while the catalytic activity tests were based on toluene oxidation process in a tube reactor with a fixed layer of catalyst. The XRD results showed only ceria in samples doped with Cu, Mn, and Zn, while other doped samples displayed the presence of additional crystallographic phases. The application of the Scherrer method revealed that the ceria crystallite sizes were between 3 and 5 nm. Approximately the same particle size could be estimated based on the TEM micrographs. Small particle sizes resulted in a high specific surface area of the prepared nanocatalysts. Ceria doped with Cu and Mn revealed substantial catalytic activity, samples with Fe, Ni and Zn showed no significant improvement of catalytic activity, while ceria doped with Co exhibited a decrease in catalytic activity for the toluene oxidation process. The obtained results are more than satisfactory and encourage us to deepen our investigation of the doped ceria nanocatalyst, specifically the Cu- and Mn-doped one, and its potential catalytic applications.

hydrothermal synthesis ; doped ceria ; nanocatalyst

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