The Preparation,Characterization And Property Of Mesoporous Hollow TiO₂/WO₃ Composite

As the electron energy level of TiO₂ is near to that of WO₃,the composition WO₃ with TiO₂ could not only promote the separation of photon-generated carriers,but also extend its photoresponse range to visible light.This will result in the improvement of its photocatalytic performance,and it can be used in environmental pollution processed.Structures of mesoporous hollow spheres have many advantages,such as low density,high specific surface area,unique reaction cavity,etc.,endowing them high adsorption capacity and excellent propagation velocity.Preparing composite material into mesoporous hollow spherical structure is conducive to the spread of the reactants and products,which can improve its photocatalytic performance.Traditional methods for preparing mesoporous hollow spheres are template method,sol-gel method,etc.,which all need to use much strong acid and organic solvents,causing high costs,environmental pollution and morphology instability.On the contrary,spray drying method is widely applied in the preparation of materials due to its advantages of continuous and easy operation and high automation degree,of which the products have high purity and their morphologies could be easily controlled.In this work,using citric acid as a complexing agent,the solution of titanyl sulfate and ammonium metatungstate?AMT?was regulated to neutral.Mesoporous hollow spheres of TiO₂/WO₃ composite were fabricated by a two-step method,i.e.,spray-drying followed by high-temperature calcination.TG-DTA?SEM?XRD?EDS and UV-Vis spectrophotometer were used to analyze the crystal phase,morphologies,surface elements and absorbance of the products.In addition,photocatalytic performance of the products were investigated by degrading methyl orange?MO?.The main conclusions of this work are as follows:?1?During the spray drying process,the inlet temperature plays a key role in forming mesoporous hollow spheres of TiO₂/WO₃ composite with the optimized temperature of 200?,while the material flow rate had little effect on the structure of final products.?2?AMT and ammonium sulfate were decomposed into water vapor and ammonia gas etc.under high-temperature calcination,leading to the structures of the spherical shells be mesoporous.In addition,the crystallinity and crystalline grain size of samples increased with the increase of calcination temperature.Rutile phase of TiO₂ started to appear at a calcination temperature of 600?;What is more,when the temperature increased to 650?,some of the spheres sticked together and then to700?,the hollow sphere morphology ultimately destroyed.?3?The absorption band of samples occurred red shift,expanding the light response range to visible light region.The color of samples changed from dark brown to light brown and finally to yellow,of which the absorbance decreased and the forbidden bandwidth got widened with the increase of calcination temperature.However,the forbidden bandwidth of the samples had little difference under different Ti/W ratios.?4?Photocatalytic performances of mesoporous hollow spheres of TiO₂/WO₃ composite were tested by using methyl orange?MO?solution as simulation pollutants.The results showed that the photocatalytic properties of the samples under the irradiation of UV were much better than that of visible light.The catalyst performs best when the calcination temperature was 470?,the material flow was 800mL/h and the molar ratio of WO₃ in the composite was 3%.The degradation of MO solution reach 99%after 2.5h,which photocatalytic efficiency is about 6 times of P25.In conclusion,the spray drying method could produce TiO₂/WO₃composite materials with unique mesoporous hollow structures,which could significantly improve its photocatalytic properties,making it has potential application value in terms of environmental protection.