| TiO2 has good photocatalytic effect in the ultraviolet region and high photoelectric conversion efficiency.It is one of the most important semiconductor materials and has been widely used in the field of photocatalysis.However,the band gap value of TiO2 is 3.0-3.2 eV,the absorption of visible light is weak,and the electron-hole pair recombination rate is high,resulting in low photocatalytic efficiency.Aiming at the limitation of TiO2,this paper modified other materials or doping elements to reduce the forbidden band width,increase the absorption of visible light,reduce the recombination rate of photogenerated electron-hole pairs,and improve the photocatalytic performance.Carbon figers(CFs)are good electron conductors that increase the separation of TiO2 photogenerated electrons and holes,thereby improving the photocatalytic effect.In this thesis,polyacrylonitrile-based carbon fiber is used as the carrier,but the combination of pure carbon fiber and TiO2 nanorod belongs to point-point contact,and the bonding strength is weak.Therefore,it is necessary to achieve a stronger surface-to-surface contact between the two,and the sol-gel process is used to cover the surface of the carbon fiber by the dip coating technique,and then the TiO2 nanorod is grown in the seed layer by hydrothermal method.The surface-surface contact between carbon fiber and TiO2 was formed,and CFs/seed layer/TiO2 nanorod composite(CFs/TiO2 seed/TiO2 nanorod,CFs/TS/TN for short)was synthesized.The effects of different synthesis conditions on the morphology and photocatalytic activity of the composites were investigated.It was found that the synthesis conditions affected the growth of TiO2 nanorods,which in turn affected the photocatalytic activity of the composites.By optimizing the synthesis conditions,the prepared CFs/TS/TN catalytic material reached 86.84%methylene blue(Abbreviated MB)degradation rate within 60 min,which is twice that of commercial titanium dioxide P25.The movement of electrons and holes in semiconductor nanomaterials is affected by quantum confinement effects,which are greatly affected by size and morphology.Hollow microspheres have large specific surface area,low density and hollow internal structure.In order to improve the photocatalytic activity of TiO2,TiO2 microspheres with mesoporous hollow structure were prepared by auxiliary template hydrothermal method.The effects of morphology of TiO2 microspheres on photocatalytic activity were investigated.It was found that the calcination temperature affects the growth of microspheres.The better the growth of spherical TiO2 is,the higher the photocatalytic activity is.The optimum conditions for the synthesis of TiO2 microspheres reached a degradation rate of 91%after 20 min illumination,while P25 had a degradation rate of only 22%.In order to futher reduce the band gap of TiO2 microspheres and improve the utilization of visible light,the effects of different N doping amounts on the morphology and photocatalytic activity of N-TiO2 microspheres were investigated.It was found that N doping can improve the size and growth of the microspheres,because urea not only acts as a doping N source,but also acts as a precipitant to accelerate the formation of microspheres and inhibit the growth of the microspheres.At an MB concentration of 200 mg/L,the optimal N-doped amount of N-TiO2 microspheres has twice the photocatalytic rate of TiO2 microspheres.In the cycle experiment of N-doped TiO2 microspheres,it was found that N-TiO2 microspheres had good cycle regeneration,and the photocatalytic degradation rate reached 96.93%in the third cycle.At the fourth cycle,the degradation rate of MB by N-TiO2 microspheres was reduced due to the decrease in N content with photocatalysis. |
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