Doped ceria nanoparticles, aimed to be used as heterogeneous catalyst for elimination of volatile organic compounds, will be prepared using hydrothermal synthesis.
A key feature of ceria is its capability of reversible redox process enabling the creation of oxygen vacancies, high oxygen mobility and oxygen storage capacity within the crystal lattice. Such properties make ceria extensively used as heterogeneous catalysts. Although primarily used as three-way catalyst in automotive industry, ceria has recently been investigated for utilization in the elimination of atmospheric contaminants such as volatile organic compounds. Nanoscale catalysts are a common goal of advanced catalyst design, so recent researches of ceria have been mainly focused on the preparation of ceria nanoparticles. One of the synthesis methods of choice for this task is the hydrothermal synthesis, since it possesses numerous advantages such as simplicity, affordability and environmental benignity, and it enables the preparation of high purity nanoparticles of desired size, morphology and large surface area, which is of particular importance for the catalytic application. Recently, it was shown that the introduction of defects by incorporation of metal ions into ceria crystal lattice yields with enhanced properties of doped ceria in comparison with pure ceria.
Therefore a systematic study of transition metals (manganese, iron, cobalt, nickel, copper and zinc) doped ceria prepared using the hydrothermal synthesis will be conducted in order to investigate the ability of transition metals to enter the ceria crystal lattice under hydrothermal synthesis conditions, thermal stability of prepared catalysts, and their catalytic activity for oxidation of model compound. On the basis of obtained results two dopant elements, most probably copper and manganese, will be selected and ceria doped with these elements should be thoroughly investigated. Beside structure, microstructure, physical properties and catalytic activity of ceria doped with various amounts of the dopant, special attention will be paid to the stabilization of crystal size and specific surface area of ceria under elevated temperatures.
For the characterization of the prepared nanocatalysts following methods will be used: X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), Fourier-transformed infra-red spectroscopy (FTIR), diffuse reflectance UV-Vis spectroscopy (DRS) and adsorption-desorption N2 isotherms. Crystallite sizes will be calculated using the Scherrer equation, particle size will be determined through TEM image analysis, band gap will be obtained utilizing Tauc’s plots, specific surface area will be calculated on the basis of Brunauer, Emmett and Teller theory, while conclusions on crystal size and specific surface area stability at elevated temperatures will be based on the grain growth kinetic analysis. Catalytic activity will be evaluated on the basis of toluene oxidation process.
The investigation will enable the gain of new knowledge on doped ceria prepared by hydrothermal synthesis. Additionally, significant results are expected in the area of grain growth kinetics and its use for the estimation of nanocatalyst crystal size and specific surface area stability at elevated temperatures. Finally, improved doped ceria heterogeneous nanocatalyst for elimination of volatile organic compounds will be prepared.