| For the application in the photodegradation of environmental pollutions, there are many barriers to limit the photocatalytic proceees for the single-component semiconductor catalyst, such as the low quantum efficiency, the low utilization rate of natural light and difficulty in recycling. In view of this, in this thesis, we mainly use the new carbon material, graphene(RGO), to modify the single-component semiconductor photocatalyst, and a series of graphene-based photocatalyst composites have been synthesized. The as-prepared products were characterized by X-ray diffraction(XRD), transmission electron microscopy(TEM), Brunauer-Emmett-Teller(BET), and vibrating sample magnetometry(VSM), etc. The photocatalytic activities were studied for the degradation of organic dyes. The main contents and results are as follows:(1) Graphene oxide(GO) can be prepared with a modified Hummers method, and P25/graphene was synthesized by a green hydrothermal method using P25 and graphene oxide as raw materials. Then, a ternary P25/graphene/Fe3O4(PGF) magnetic nanocomposite has been successfully synthesized by decorating Fe3O4 nanoparticles on the P25/graphene through a hydrothermal reaction. It is investigated that the degree of photocatalytic activity for the degradation of Rhodamine B(Rh B), methylene blue(MB), and methyl orange(MO) as model pollutants. The results show that the as-synthesized sample exhibits high photocatalytic activity towards various dyes, and can be easily recycled by normal magnet due to the existence of Fe3O4 nanoparticles. In addition, the stability and reusability of the PGF composites were examined by repetitive use of the catalyst, and did not exhibit a significant loss of activity after five photodegradation cycles.(2) A facile one-step hydrothermal synthesis approach has been developed to fabricate Ce O2/graphene composites with Ce(NO3)3·6H2O and GO. The effects of various synthesis parameters such as reaction solvent, the concentration of PVP, reaction time, reaction temperature are thoroughly investigated. It is found that when the solvent is C2H5 OH,the concentration of PVP is 2.5 g/L, the reaction temperature is 120℃, the reaction time is 24 h, it is the optimal conditions for synthesis of Ce O2/graphene composites. Then, the photocatalytic performance of the Ce O2/graphene composites is measured for the degradation of Rhodamine B. The results show that we could get Ce O2/graphene composites with the photocatalytic activity, which is more activity than pure Ce O2 nanoparticles increased by more than 60%.(3) Ce O2 particles were synthesized by a green hydrothermal method using Ce(NO3)3·6H2O. Then, the ternary nanocomposite of Ag/Ce O2/graphene, in which reduced graphene oxide sheets and Ce O2 particles are decorated with Ag nanoparticles, is synthesized by in vigorous ultrasonication for Ce O2 nanoparticles on graphene oxide sheets, following by the electron beam irradiation method for co-reduction of Ag+ and GO. The photocatalytic properties of the Ag/Ce O2/graphene ternary hybrid nanomaterials were evaluated with the degradation of Rhodamine B, and possible mechanisms for the enhanced photocatalytic performance were proposed. The results reveal that the presence of Ag particles can significantly improve the catalytic activity, due to the introduction of Ag particles expected to serve as an efficient acceptor for the photogenerated electrons, thus significantly suppressing charge recombination. The possible mechanisms indicate that ·OHads pathways play an important role in the process of oxidation.Based on the above, owing to the presence of graphene, the photocatalytic performance of the composites has been greatly improved. The main reason is that the electron transfer between the semiconductor catalyst and graphene plays a key role in suppressing charge recombination and the photodissolution of magnetic materials, and the loading of graphene increases the specific surface area of the composites promoting dyes adsorption. |
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