| In this thesis, using surfactants as structure-directing agents, urea as precipitator, and manganese sulfate (MnSO4·H2O) as the source of manganese, a serials of micro-and nano-MnOx crystals with different morphologies and structures had been successfully synthesized by controlling synthetic parameters. At the same time, the obtained octahedral Mn3O4 nanocrystals were investigated systematically on the catalytic degradation of methylene blue (MB).Scanning electron microscope(SEM), transmission electron microscopy(TEM), X-ray scattering techniques(XRD), Raman, Fourier transform infrared spectroscopy (FT-IR), N2 adsorption-desorption and DSC-TG were used to investigate the structures and morphologies of the synthesized samples, such as crystalline, surface area, pore size distribution and thermal stability. The size and shape of the micro- and nano- crystals were easily controlled by varying the synthetic parameters. The results indicate that the average crystallite size of octahedral Mn3O4 nanocrystals is related to the reaction time in the system of 200 mL water volume, which increased from 151.5 nm to 238.3 nm and to 390 nm corresponded to the reaction times of 8 h,16, and 24 h, respectively. The octahedral Mn3O4 nanocrystals could be gradually dispersed very well by increasing reaction temperature (from 80℃to 150℃) and using CTAB/PVP as a mixture surfactant, while in the presence of P123, the nanocrystals were transformed from octahedron to sphere-like shapes. When the manganese source was changed, the octahedral nanocrystals were altered to polyhedron and nano-rods. The crystals were transformed from Mn3O4 to Mn2O3 by calcinations at 600℃for 4 h, and in our opinion, the defects of the this system is the lower morphology yield. And in the system of 180 mL, the yield of octahedral shapes was almost 100% at 85℃. However, the shapes were almost Mn2O3 micro-cubic structure at 120℃.It was presented that octahedral Mn3O4 was H2O2-assisted catalytic degradation of MB, which was synthesized in extremely dilute solution by soft template self-assembly. The influence on degradation of MB at reaction temperature, the initial concentration of MB, H2O2 content, catalytic loading, and different morphologies of Mn3O4 was investigated systematically. The results indicated that the most important factions involved reaction temperature, H2O2 content, and different Mn3O4 morphology. The degradation of MB was 99.68% under the optimum experiment condition, however, the initial concentration of MB and catalyst contents had no obviously influenced on the degradation. Meanwhile, the degradation products of MB dye were analyzed by ion chromatography, which contained 2.13μmol·L-1 SO42- and 6.94μmol·L-1 NH4+, and the benzene structure of MB vanished in the analysis of FT-IR. After separating the catalyst from the solution, the analysis of XRD, EDX, and SEM on solid product coming from the evaporation of reaction solution showed that it contained Mn, P,O and H, and the shapes were changed along with different pH. Moreover, the catalytic activity was still high after multiple circulation use, whose degradation was still above 90%.Through the system investigation of MnOx micro- and nano-structure, in order to prove the universality of the method, we have performed a series of explorative research for other transition metal oxides nanostructure in the same sys. In the sys of 200 mL water volume, we used urea as precipitator and surfactants as structure-directing agents, added some metallic salts (Co(NO3)2·6H2O, CdCl2·2.5H2O, Cu(NO3)2·3H2O), reacted at 85℃for 1 d, and obtained conresponded transition metal oxides (Co3O4, CdO, CuO) after a certain calcinations perature, which was suitable for the synthesis of FePO4 nanomaterials. Meanwhile, we used metal ions and organic materials as forming metal-organic ligands, which were calcinated at 400℃in the result of conresponded transition metal oxides.
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