Study On Preparation And Properties Of Titanium Dioxide/Graphene Composites

As a photocatalyst,TiO₂ is widely used in the fields of degradation of organic pollutants,purification of the environment,and self-cleaning due to its high chemical stability,low cost,low energy consumption,safety and non-toxicity.However,the shortcomings of TiO₂ with high band gap energy?about 3.2eV?and low utilization rate of photogenerated electron-hole pairs limit the application of TiO₂ as a photocatalyst in industry.In order to ensure that TiO₂can make full use of its advantages in practical industrial applications and improve the photocatalytic activity of TiO₂,the research mainly focuses on reducing the band width of TiO₂,increasing the utilization of photogenerated electron-hole pairs and improving its photocatalytic performance.First,using self-made graphene oxide?GO?as a template,TiO₂ is grown in situ by the sol-gel method,and then heat treatment,reduced graphene oxide/titanium dioxide?RGO/TiO₂?is prepared.The materials are characterized,and a photocatalytic experiment is performed using a methylene blue?MB?solution to simulate printing and dyeing wastewater.The effect of RGO content on the photocatalytic reaction is discussed.The results show that TiO₂ is still anatase in RGO/TiO₂ composites,and its morphology is mainly small particles,which are uniformly and densely supported on the RGO sheets.The RGO/TiO₂ composites absorption sidebands show a red shift phenomenon,and the band gap energy is reduced to about 3.0 eV.In the photocatalytic experiment,3%RGO/TiO₂ composites has the best photocatalytic effect.It almost completely degrades MB solution under ultraviolet light,and the visible degradation rate increased to 2.20 times of TiO₂,which shows that the composite of RGO effectively improves the photocatalytic activity of TiO₂.Secondly,Pr/TiO₂ and Gd/TiO₂ photocatalysts are prepared by doping TiO₂ with rare earth Pr and Gd.The products are characterized,and the MB solution is used to simulate the printing and dyeing wastewater for photocatalytic experiments.The effects of the amount of rare earths on the photocatalytic reaction are discussed.The results show that doping Pr and Gd does not affect the crystal form of TiO₂,nor does it change the morphology of TiO₂.The absorption sidebands of Pr/TiO₂ and Gd/TiO₂ show a red shift phenomenon,and the band gap energy of both products is reduced to about 3.0 eV.In the photocatalytic experiments,the degradation effect is best when the doping amounts of Pr and Gd are 1.0%and 1.5%,respectively.The equilibrium degradation rate under ultraviolet light is increased to 1.45times and 1.64 times of TiO₂ respectively,and the equilibrium degradation rate under visible light is increased to 1.67 times and 1.73 times of TiO₂,respectively.It shows that rare earth Pr and Gd doped TiO₂ can effectively improve its photocatalytic activity.Finally,based on the first two parts of the experiment,RGO-Pr/TiO₂ and RGO-Gd/TiO₂composites are prepared by combining rare earth doped TiO₂ and RGO.The samples are characterized,and the MB solution is used to simulate the printing and dyeing wastewater for photocatalytic experiments.The effects of the amount of rare earth doping on the photocatalytic reaction are discussed.The results show that the morphology of the composites is that the rare earth-doped TiO₂ particles are uniformly supported on the stacked RGO sheets,and the TiO₂ is still anatase.The red shift phenomenon of the absorption sidebands of the composites is more obvious,and the band gap energy of both products is greatly reduced to about 2.8 eV.In photocatalytic experiments,the best products are RGO-1.0%Pr/TiO₂ and RGO-1.5%Gd/TiO₂ composites.The both equilibrium degradation rate of them under ultraviolet light is increased to about 1.76 times of TiO₂,and the equilibrium degradation rate under visible light to 2.46 times and 2.48 times of TiO₂ respectively.There is a synergy between the rare earth ions and RGO,which reduces the band gap energy of TiO₂ to a greater extent,thereby significantly improving the photocatalytic performance of the material.