| Since the photocatalytic effect of semiconductors was discovered by Fujishima et al.in 1972,researches on semiconductor photocatalysis have been fully developed and widely used in various photocatalytic fields.Semiconductor photocatalytic technique has also been an important approach to treat organic pollutants in waste water.Among various semiconductors,Ti O2 is one of the best photocatalysts in waste water treatment due to its high chemical stability and oxidation ability,which can almost degrade all organic pollutants without selectivity.However,it still suffers from some drawbacks such as low phase transition temperature?450-550oC?,lack of visible light response,low photon efficiency,difficult to separate after reaction,and easy agglomeration.Therefore,the modification of Ti O2 based photocatalyst has been studied hotspot.In order to improve the practical application of Ti O2 nanomaterials,this paper uses low-cost,environmentally friendly Si O2 and visible light responsive g-C3N4 to modify Ti O2 nanomaterials.On the basis of the composite modification of Si O2 and g-C3N4,aiming at the problems that can be expanded and improved in the existing system,a new strategy and method for the preparation of the composite system were explored around the structural control and simple preparation of the composite catalyst,and the performance of the composite photocatalyst for the degradation of organic compounds was studied.The details of our work are listed below:1.A series of Si O2@Ti O2 microspheres with different core diameters were prepared by the sol-gel method,and Ti O2 was coated on the Si O2 microspheres.The size effect of Si O2 core on the grain growth process was discussed in detail.After treated at 700oC,Ti O2 still maintains anatase phase with high crystallinity.As the diameter of Si O2 increases,the grain size of Ti O2 and the catalytic activity of the catalysts gradually increase.Rare earth ions were doped in the Ti O2 shell,and the effects of the doping concentration of rare earth ions on the crystal growth process,phase transition process and catalytic performance of Ti O2 were studied.It was found that low concentration Eu3+doping?2%mol?have increased the catalytic activity,and high concentration Eu3+doping?18%?have accelerated phase transition process of Ti O2.2.To further investigate the effect of Si O2 modifying on the properties of Ti O2crystals,Si O2-Ti O2 hybrid nanofibers were synthesized by electrospinning approach.The spinning precursor solution was composed of tetraethyl silicate?TEOS?and tetraethyl titanate?TBOT?with different molar ratio to investigate the effect of Si O2content on the properties of the composite fibers.When the molar ratio of Si/Ti in the composite gradually increases,the effect of Si O2 on inhibiting the phase transition of Ti O2 becomes more obvious.When the molar ratio of Si/Ti increases to 5%,the phase transition temperature increases from below 600oC to 600-700oC.At the same time,it was found that Si O2 plays an important role in maintaining the mesoporous structure of Ti O2 crystals.The results show that the catalytic activity of Si O2 modified samples is significantly enhanced compared with that of pure Ti O2,and the catalytic activities of the samples 600-2%and 700-2%are 3.7 and 3.2 times that of pure Ti O2samples calcined at the same temperature,respectively.3.By combining electrospinning method with vapor deposition approach,a kind of Ti O2@g-C3N4 core-shell nanofibers with good interface contact was successfully synthesized.The growth process and mechanism of g-C3N4 on Ti O2 fibers were studied in detail.The effect of the amount of g-C3N4 loaded on Ti O2 fibers of the catalytic performance of the samples was investigated.It is found that there is heterostructure existing between Ti O2 and g-C3N4,and the Rhodamine B degradation efficiency was 4.0 and 2.7 times higher than that of pure g-C3N4 and Ti O2,respectively. |
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