The Preparation Of Graphene-Based TiO₂ Nano-Catalysts And Their Photocatalytic Performance

Photocatalysis is an effective way to solve the environmental crisis.TiO₂,the most typical photocatalyst,has been extensively studied due to its physical and chemical stability,high reactity,low toxicity and cheapness.However,TiO₂ has low photocatalytic efficiency as the result of its wide band gap（Eg=3.2eV）,which leads to the low solar energy utilization and high recombantion rate of photogenerated electrons-holes（e^-/h⁺）.It will be a key factor to effcetivly utilize solar energy that looking for new photocatalysts and extending photoresponse area of typical photocatalysts.We mainly use the new carbon material,grapheme（GR）,to modified TiO₂ as the new graphene-based photocatalyst.The obtained nanocomposites were characteristiced by XRD,FTIR,XPS,SEM,TEM,HRTEM,TGA,UV-vis,EPR and PL,and were evaluated the photocatalytic activity by photodegradation of rhodamineand 6G and chromium（Cr）-containing wastewater.Specifics as follows:a.The graphite oxide（GO）was prepared by the modified Hummers method.The characterization results showed that the graphite powder was successfully oxidized to GO and the quality was relatively good.The TiO₂/rGO composite was prepared by the in-situ photoreduction strategy.Then,it was used to purify the dyeing wastewater（rhodamine 6G）and calculated via kinetic fitting.Through the doping of rGO,the photocatalytic rate of TiO₂/rGO increased about 3.5 times compared with that of single TiO₂.The reasons for the increase of photocatalytic performance caused by the doping of rGO are as follows:1)increase of adsorption capacity;2)increase of absorbed light intensity;3)extension of light absorption range;4)the lower electron-hole pair recombination rate;b.Using tetrabutyl titanate（TBOT）as TiO₂ precursor,ultra-dispersed TiO₂@rGO nanocomposite catalysts were prepared through one-step Sol-Gel chemical in-situ method,and their degradation and decolorization of dyeing wastewater was investigated under the visible light irradiation.The photocatalytic activity of methylene blue was found to have been significantly improved by rGO addition.Methylene blue was completely degraded within 3h,and it was found that TiO₂ was uniformly formed on the surface of graphene.It is more conducive to exerting the structural advantages of graphene,which is beneficial to further reduce the e^-/h⁺pair recombination probability;c.Ag/TiO₂/rGO graphene-based composite were prepared by in-situ photo-deposition using noble metal Ag surface plasmon effect and commercial P25 as TiO₂ precursor.Then,it was used in Cr（VI）heavy metal wastewater treatment.It was found that the photocatalytic activity of the obtained complex was further improved comparing to TiO₂/rGO;The dissertation focuses on the modification of TiO₂ semiconductor photocatalysts by graphene and its derivatives.And,the research content mainly focuses on the preparation methods of graphene-based TiO₂ composite nanocatalysts and their application in environmental pollution control.The reason why the TiO₂photocatalytic performance was enhanced via graphene materials addition was discussed.The effects of different preparation methods on the properties of graphene-based TiO₂ composites were studied and discussed.And,the mechanism of pollutant degradation in the photocatalytic system of graphene-based TiO₂ was briefly analyzed.