Study On Preparation And Properties Of Graphene And Graphene-TiO₂ Composite

Titanium dioxide?TiO₂?is a photocatalyst that is widely used at present.The utilization rate of natural light is low.Generally,it exists in powder form,which is easy to be lost and has poor recycling.Therefore,for large-scale industrial application of TiO₂,it is necessary to modify TiO₂ and load it with high efficiency and stability.Graphene?GR?has excellent optical,electrical,and mechanical properties and a large specific surface area.Combining it with TiO₂ can reduce the band gap of TiO₂,promote electron migration,and enhance the photocatalytic activity of TiO₂;Carrying on the load can effectively overcome the problems of easy aggregation and difficult recovery of powder.Based on the above research background,this study first used flake graphite as the raw material and sodium cholate?NaC?as the intercalator to prepare GR with few layers and fewer defects,and studied the effect of shear speed on GR peeling effect;then GR and anatase nano-TiO₂ were used as raw materials to prepare GR-TiO₂ composite materials.The photocatalytic properties of GR-TiO₂ composite materials prepared by three different methods of simple stirring,ultrasonic treatment and hydrothermal reaction were studied;GR-TiO₂films were prepared with different binders,the effects of different binders on GR-TiO₂ film properties were investigated,and the photocatalytic performance of the obtained films was tested.The main findings are as follows:?1?GR was prepared by high-speed shearing method.After a series of test and characterization analysis of Raman,SEM,infrared?FT-IR?,it was found that flake graphite can be peeled off by high-speed shearing in aqueous solution with sodium cholate GR was prepared,in which the ratio of flake graphite to NaC was 3:1,the rotation speed was 9000r/min,the shear time was 1h,the concentration of the prepared GR was about 0.059mg/mL,and the number of layers was mostly 2 layers.The yarn-like morphology gathered lightly,with some curls around the edges.Isopropanol-assisted peeling method was used to transfer GR to PET film successfully.?2?GR-TiO₂ composite material was prepared with GR and nano-TiO₂ as raw materials.Through analysis and characterization and photocatalysis simulation experiments,it is found that GR and TiO₂ are combined and reduced by some oxygen-containing groups.GR doping makes the absorption edge of GR-TiO₂ red-shift,The absorption of visible light is significantly enhanced,Increased utilization of visible light.?3?Three different substrates and three different binders were used to prepare GR-TiO₂films.The effects of different substrates and binders on the film-forming effect and photocatalytic performance were discussed respectively.Through comparative analysis of surface morphology,loading,firmness and photocatalytic effect,it is concluded that the GR-TiO₂ composite material prepared with PDA as the binder and PET as the substrate has the best photocatalytic effect and overall degradation The rate reached 89%,and the degradation rate per unit area reached 3.56%,much higher than others.PET has excellent light-transmitting properties and is firmly combined with composite materials.PDA can also promote photo-generated electron migration.Together with GR,it improves the photocatalytic performance of TiO₂.?4?In the case of determining the best binder and substrate,the GR-PDA-TiO₂ composite film was prepared by three different processes,and the effects of different processes and loading on their photocatalytic properties were discussed respectively.The best preparation process is:400mgTiO₂,10mgDA,50mLGR solution,adjust the pH to 8.5,heat and stir at 90r400r/min for 3h,take the product after filtration,cleaning and drying,dissolve in absolute ethanol,the concentration is 10mg/mL,spray on On the PET substrate,the average load is0.596mg/cm².The degradation rate of methyl orange reaches 78%,and the different loadings have a greater impact on its photocatalytic performance.Within a certain range,the loading amount can promote its photocatalytic performance.When the loading is too much,the lower GR-PDA-TiO₂ will be blocked,resulting in reduced photocatalytic activity.