| In this study, due to the TiO2 has low light absorption in the visible region, and it is inconvenient to isolate and recover, we design three different nanocomposites: Fe3O4@C@TiO2, Fe3O4@C@TiO2-Ag2 O and TiO2-Ag3PO4, the main purpose is to get the recycling photocatalyst, suppress the recombination of photogenerated electron/hole pairs, extend absorption light response range and enhance the photocatalytic activity of TiO2. The as-synthesized nanocomposites were characterized by Transmission electron microscopy(TEM), Scanning electron microscopy(SEM), X-ray diffraction(XRD) and the magnetization measurement(SQUID). To investigate the photocatalytic of the different photocatalysts, we selected photocatalytic degradation of MB as a model reaction(under the UV-light or Visible-light irradiation), the main contents are as fllows:(1) Through the solvothermal method, we prepared the Fe3O4 microspheres with a diameter of 300 nm. The magnetite microspheres were coated with a thin layer of carbon by the polymerization and carbonization of glucose through a hydrothermal reaction, the thickness of the carbon was about 10-20 nm, and the Fe3O4@C microspheres had excellent aqueous dispersibility. During the sol-gel process, because of the surface of the Fe3O4@C microspheres turned to being negatively charged, the TiO2 shell could be facilitated via the electrostetic interaction. Finally, we synthesized the Fe3O4@C@TiO2 core-shell composite photocatalysts with fast magnetic separation, and the thickness of TiO2 shell could be controlled. The carbon layer between the magnetic particle and the titania shell can effectively protect from the electron interaction or photodissolution of Fe3O4. Under the UV-light irradiation, the experiment of photocatalytic degradation of MB showed that the degradation efficiency of Fe3O4@C@TiO2 reached 95.6% in the 8 min. After the photocatalytic experiment was carried out five times, the degradation efficiency was still achieved 93.6%.(2) Based the result of the last work, the Fe3O4@C@TiO2-Ag2 O nanocomposites were successfully prepared via a co-precipitation method. The structures of the nanocomposites were characterized by TEM, SEM, XRD and XPS. The UV-vis absorption spectrum showed that the as-synthesized nanocomposites exhibited strong capability of light absorption in the range of 200-800 nm. From the magnetization curves of Fe3O4@C@TiO2-Ag2 O, we can see that the nanocomposites still show strong magnetization to be separated easily from solution with the help of an external magnetic force. Under the UV-light irradiation, the experiment of photocatalytic degradation of MB showed that the degradation efficiency of Fe3O4@C@TiO2/Ag2O(4:1) was highest, and the first-order degradation rate(0.5627 min-1) was higher than commercial photocatalyst Degussa P25(0.4268 min-1). Futhermore, the composites showed a good photocatalytic performance under visible-light irradiation, and the degradation efficiency of Fe3O4@C@TiO2- Ag2 O reached 91.7% in the 70 min.(3) The spindle-shaped nanoporous anatase TiO2-Ag3PO4 heterostructure have been successful prepared via the hydrothermal method and an in situ precipitation method. The BET results showed that the spindle-shaped TiO2 had a nanoporous structure, which can provide very beneficial sites to adsorb the positively charged silver ions(Ag+), and it will limit the growth of Ag3PO4 particles. The structures of the nanocomposites were characterized by TEM, SEM, and the elements of the nanocomposites were characterized by EDX, XPS. From the UV-vis absorption spectrum, we can see that the TiO2-Ag3PO4 exhibited stronger capability of light absorption than TiO2 in the range of 400-800 nm. Under the visible-light irradiation, the Ti O2-Ag3PO4 heterostructure composite exhibited a higher activity for the degradation of MB than Ag3PO4 particles, which was nearly 1.8 times of Ag3PO4 particles and the degradation efficiency reached 93.7% in the 12 min... |
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