The mixed oxides SiO2/MxOy obtained by the sol-gel process, designated as composites, usually combine both mechanical and chemical properties of silica gel with the chemical properties of metal oxide (MxOy), showing properties such as: high degree of dispersion and homogeneity of metal oxide particles in the silica matrix, as well as high mechanical and chemical resistance. The goal of this work was to prepare and characterize materials in the system SiO2/Mn xOy obtained by the sol-gel process, using different concentrations of Mn (II) precursors (acetate or nitrate). The technique of X-ray fluorescence showed that the concentration of metal oxide in the materials is dependent on the precursor used and its concentration, ranging from 9.4% up to 20.9% by mass. The highest concentration of manganese oxide was obtained when (CH3CO2)2Mn.4H2O was used as precursor. The infrared spectra indicate that the network of SiO2 is not disturbed by the increase in the quantity of manganese oxide, suggesting that the Mn xOy is dispersed on the surface of the silica matrix. The X-ray diffraction showed the low crystallinity of these materials. However, there is a change in the XRD on 2θ = 35.7(0) when the material is heated to 400 0C, probably due to the formation of Mn3O4 crystallites. The proposed synthesis method for materials SiO2/Mn xOy is reproducible. Application of these materials as electrodes for the reduction of O2 was evaluated and it was found that the electrocatalytic activity of these materials can be increased by heating them at 400 0C.
Sol-Gel; Mixed Oxide; Silica Gel; Manganese Oxide; Composite
