Preparation Of Modified Photocatalyst Based On TiO₂ And Photocatalysis Research

Semiconductor TiO₂photocatalysts with many excellent properties have become widely used in catalysis,disinfection,sterilization and so on.However,its practical application is constrained due to some of its own characteristics of TiO_2.Aimming at the existence of TiO₂photogenerated electron-hole pairs are readily recombined,small specific surface area,low photocatalytic activity under visible light in photocatalytic reaction.In this thesis,TiO₂was modified by reduced graphene oxide（RGO）and regulating the crystal face to improve the photocatalytic performance.The main study are as follows:（1）Graphene oxide（GO）was prepared from graphite powder via Hummers method,and then RGO/TiO₂composite photocatalyst was prepared via one step hydrothermal method.The optimal preparation conditions were determined:the doping amount of GO was 3%,hydrothermal temperature was 180℃and reaction time was 9 h.The photocatalysts were characterized by XRD,UV-vis DRS,FT-IR,BET and SEM techniques.The results showed that GO was reduced to reduced graphene oxide（RGO）and TiO₂with small spherical structure was grown on the RGO surface,and the sample possessed anatase phase with bandwidth of 3.02 e V,specific surface area of 101 m²/g and average pore diameter of 6.61 nm.The degradation rate of methylene blue solution（MB,15 mg/L）was 97.8%under high-pressure mercury lamp（125 W,main wavelength is 365 nm）irradiation for 120 min,at the same time the photocatalyst can be recycled 5 times,degradation rate was maintained 95.8%,this showed good photocatalytic activity and reusing stability.（2）The{001}TiO₂photocatalyst were synthesized by solvent thermal from raw materials of HAc,NH₄F and Ti（OBu）₄.The optimal reaction conditions were:reaction temperature and the reaction time were 200℃and 24 h respectively.The TiO₂mesocrystals（{001}TiO₂-1）with exposed{001}facets was obtained when the molar ratio of F:Ti to 1:1（R_f=1）,which possessed spherical-like structure and particle size between 100-200 nm,its bandwidth was 3.21 e V,specific surface area was 88.6 m²/g and average pore diameter was 11.1 nm.The degradation of MB solution（10 mg/L）,rhodamine B solution（Rh B,10 mg/L）,norfloxacin solution（Nor,20mg/L）and tetracycline solution（Tc,20 mg/L）reached 97.7%,94.7%,90.9%and 90.3%respectively under high-pressure mercury lamp irradiation for 60 min.The TiO₂single crystal（{001}TiO₂-4）with exposed{001}facets was obtained when the molar ratio of F:Ti to4:1（R_f=4）,which possessed uniform flat shape structure with the size of 1μm,its bandwidth was 3.19 e V,specific surface area was 47.2 m²/g and average pore diameter was 12.2 nm.But the photocatalytic performance was slightly worse than that of{001}TiO₂-1 at the same photocatalytic conditions,the degradation rate of dyes solution and antibiotics solution were only about 50%after 60 min irradiation.（3）The{001}TiO₂-4 photocatalyst possessed good morphology,but the photocatalytic activity was low.In order to improve its activity,it was modified by RGO.The RGO/{001}TiO₂composite photocatalyst was obtained by reflux method by reducing GO to RGO with ascorbic acid as reducing agent.The results showed that photocatalyst possessed anatase phase with the bandwidth of 2.92 e V,specific surface area of 189 m²/g and average pore diameter of 5.25 nm.Compared with the pure{001}TiO₂-4,the bandwidth was reduced by0.27 e V,the specific surface area was increased by 4 times,the average pore diameter was reduced by 2.3 times after modified.The degradation rate of MB solution（20 mg/L）can be up to 92.7%under Xenon lamp（150 W）after 120 min.And the degradation reaction rate follows the first-order reaction dynamic model,the degradation rate constant ka was 0.0164,which is about 3.2 times of{001}TiO₂-4.The degradation rate of Nor solution and Tc solution were88.9%and 88.7%,and RGO/{001}TiO₂had excellent cycle stability,degradation rate of MB solution and Tc solution still remaining at 89.1%and 87.2%after recycle 5 times.Through active group capture experiments,the results showed that the photogenerated electron and hole played the leading role in the photocatalytic degradation process.