| The environmental pollution and shortage of energy is becoming a focus subject ofworld. The photocatalysis technique of semiconductor has the advantages of low reactiontemperature, cleaning thoroughly, green energy, strong oxidation, which has a promisingapplication prospect in environmental and sources of energy fields. TiO2is common usedphotocatalyst and has the characteristics of high chemical stability, non-toxic and low cost.However, its large band gap and small size lead to some shortcomings, such as the lowsolar energy utilization rate, difficulty to be separated, the low reaction of quantumefficiency and etc.. In this thesis, we proposed some methods to solve these problems.Graphene, a single layer of sp2-bond carbon, is a nearly ideal2D material. It hasattracted a great deal of scientific interest and possesses potentially applications in variousfields, such as composites materials, batteries, solar cell and photocatalysts, due to itsunique electronic property, high transparency, flexible structure, large specific surface areaand good thermal conduction. Among that, the good electronic conductivity and largespecific surface area made graphene an excellent catalyst carrier. It must be enhance thephotocatlyic activities effectively with introducing graphene into semiconductor materialto arouse the synergistic effect of graphene and semiconductor material.In this thesis, reduced graphene oxide (RGO)/TiO2and magnetic separable and visiblelight responsive Fe2O3/TiO2/graphene composites were synthesized by one-stepcombustion method, or microwave assistant combustion method. X-ray diffraction (XRD),transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fouriertransform infrared spectroscopy (FTIR) and UV-visible-near infrared spectrophotometer(UV-vis) were used to characterize the phase structure, morphology and photocatalyticproperties of the samples.RGO/TiO2composites with enhanced photocatalystic activity for methyl orange weresynthesized by a simple one-pot combustion and microwave-assistant combustion method.Through controlling the combustion temperature or the microwave irradiation time, thesynthesis of TiO2, reduction of graphene oxide (GO) and combination of TiO2and GO were simultaneously achieved. The as-synthesized photocatalysts exhibit excellentphotocatlyic activities. This is associated with the graphene, which has the excellentadsorption ability facilitates the diffusion of MO molecule from solution to the surface ofcatalysts, and thus improves its photocatalystic performance. Moreover, the existence ofgraphene promotes the photo-generated electrons transfer and reduced chargerecombination, which is also beneficial for the photocatalytic activity.The visible-light responsive magnetic Fe2O3/TiO2/graphene (GTF) compositesphotocatalysts have been synthesized by a simple one-step combustion method. Theexperimental results show that the composites can be obtained by controlling thecombustion temperature. And the thermal reduction of GO, formation of magnetic Fe2O3and combination of them were one-pot achieved. The as-synthesized composites not onlyexhibit excellent visible light activity, but also possess a stability of photocatalyst. Thereare three reasons for the enhanced photocatalytic activity of composites. Firstly,photo-generated electrons can be effectively transferred from TiO2to graphene, whichprevents the recombination of electron and hole. Secondly, the photo-generated electronstransfer from the CB of TiO2to low energy Fe2O3clusters, which also made chargeseparation and recombination suppression. Finally, Fe2O3has a low band gap and can beexcited to generate electron–hole pairs under visible-light irradiation. Above all, thesemade our composites possess excellent photocatlyic activities. |
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