MnO x /ZrO2 gel-derived materials for hydrogen peroxide decomposition
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Manganese-yttrium-zirconium mixed oxide nanocomposites with three different Mn loadings (5, 15 and 30 wt%) were prepared by sol–gel synthesis. Amorphous xerogels were obtained for each composition. Their structural evolution with the temperature and textural properties were examined by thermogravimetry/differential thermal analysis, X-ray diffraction, diffuse reflectance UV–vis spectroscopy and N2 adsorption isotherms. Mesoporous materials with high surface area values (70–100 m2 g−1) were obtained by annealing in air at 550 °C. They are amorphous or contain nanocrystals of the tetragonal ZrO2 phase (T-ZrO2) depending on the Mn amount and exhibit Mn species with oxidation state higher than 2 as confirmed by temperature programmed reduction experiments. T-ZrO2 is the only crystallizing phase at 700 °C while the monoclinic polymorph and Mn3O4 start to appear only after a prolonged annealing at 1,000 °C. The samples annealed at 550 °C were studied as catalysts for H2O2 decomposition in liquid phase. Their catalytic activity was higher than that of previously studied Mn/Zr oxide systems prepared by impregnation. Catalytic data were described by a rate equation of Langmuir type. The decrease of catalytic activity with time was related to dissolution of a limited fraction (up to 15%) of Mn into the H2O2/H2O solution.
KeywordsSol–gel MnOx/ZrO2 nanocomposites H2O2 decomposition Green propellant
The research leading to these results has received funding from the European Community’s Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 218819.
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