Preparation And Catalysis Activity Of TNTs/Graphene Composite

Some organic composites which are difficult to degraded can bemineralized to carbon dioxide and water by using TiO₂. Due to its highreaction rate, high efficiency and non-toxic, TiO₂photocatalysis becomes anew technology with promising prospect to purify water. However, TiO₂possesses a wide band-gap and hence responses to UV-light only, whichlimited the efficiency of utilizing sun-light. Therefore, some approachesincluding doping and sensitization were proposed to endow the TiO₂withvisible-light activity. In this paper, graphene was used as sensitizer tohybridize with TiO₂. The graphene modified TiO₂photocatalysts possessexcellent activities in the visible-light region, which result from thepresence of graphene.A series of graphene/titanate nanotubes （TNTs） photocatalysts weresynthesized by hydrothermal method and characterized by XRD、TEM、FTIR. The interaction between graphene and TNTs, influence from theamount of graphene and reaction temperatures to the crystal structure ofthe catalysts were analyzed. The results show that graphene and TNTswere effectively combined during the hydrothermal reaction. The variedcontents of graphene and preparation temperatures only influence the lightactivities of the fabricated composite but not significantly affect the crystalstructure of the photocatalysts. In addition, the results of UV-vis diffusereflection spectra and XPS confirm the extension of light response range.The visible-light activities of as-prepared composite photocatalystsoriginate from the sensitization of graphene.The photocatalytic activities of all catalysts under sunlight irradiation were researched. The results demonstrate that the photocatalytic efficiencyof all photocatalysts were better than70%after12hours illumination. Thebest sample almost fades RB solution completely, and the degradationefficiency is as high as88%.By using xenon lamp as the light source, the photocatalyticperformances of reused catalysts under visible light illumination werestudied, as well. No significantly decrease can been observed for thephotocatalytic activities when the photocatalysts were employed for threetimes. And the reuse performances of the catalysts were not affected by thechange of graphene amounts and temperatures, indicating the high stabilityof the catalysts. And we researched the photocatalytic performance fromthe influence of organics concentrations. The results suggested that thephotocatalytic efficiency of the catalysts decrease with the increasedconcentration of organics, and the value falls to about70%in the case ofthe organics with low concentration.The graphene modified titanate nanotubes was coated on conductingglass to prepare cathode of the photoelectric catalytic reaction. Theplatinum electrode was adopted as the anode. The photocatalyticperformances for the degradation of RB and phenol under visible lightillumination were analyzed. These prepared photocatalysts all exhibitedgood visible light response to degrade pollutant. Under the sametemperature condition, the sample with5wt%graphene possesses the bestphotocatalytic activities, and followed the sample with1wt%graphene andthe sample with10wt%graphene. In the degradation of RB experiments,the efficiency of using the best sample reached93%, while the efficiencyalso reached53%in degrading phenol. It is found that the photocatalyticactivity is related with the hydrothermal temperature, and the performancesof the catalysts degrade with the increasing temperature. The out-current inthe catalytic system could fast transfer the photogenerated electron toplatinum electrode, inhibit the recombination of the electron-hole pairs,and thus evidently enhance activities photocatalysts to degrade RB and phenol.