Research On Full Spectrum Photocatalytic Activity Of Fluorine Doped Ammonium Tungsten Bronze-based Nanomaterials

with the development of social economy,air pollution and water pollution are the main problems which mankind are facing.Photocatalysts can not only make full use of the green renewable energy sunlight,but also photolysis hydrogen production,degradation of organic and inorganic pollutants in water.Semiconductor photocatalyst provides a clean and feasible solution for water and air pollution.At present,most photocatalyst materials have high responsiveness to ultraviolet and visible light,but the high energy near infrared light in solar spectrum has not been effectively utilized.Therefore,the development of photocatalysts with high response efficiency to near infrared light or full spectral response is still a hot research topic.Tungsten bronze is a kind of direct semiconductor material with a band gap of2.5-2.8eV.It can theoretically generate electrons and holes by ultraviolet and partial visible light excitation,degrade pollutants and achieve photocatalytic performance.It also has good near-infrared absorption performance.Its band gap is large and can not be directly stimulated by near-infrared light to generate photogenerated electrons and holes,but through ion doping and noble metal loading may increase the number of electrons and holes in the material under near infrared light,thus making it possible to develop a photocatalyst with full spectral response.In this paper,the near infrared photocatalytic activity of fluorine-doped ammonium tungsten bronze was improved by changing its composition and structure.The separation of photogenerated electrons and holes was enhanced by noble metal loading,so as to further improve the full spectrum photocatalytic activity of fluorine-doped ammonium tungsten bronze.The specific content includes the following parts:（1）Ammonium tungsten bronze and fluorine-doped ammonium tungsten bronze nanoparticles were synthesized by solvothermal synthesis.The effects of F-doping on the composition,morphology and photoelectric properties of ammonium tungsten bronze were investigated.Research shows that F doping did not change the ammonium tungsten bronze phase is still hexagonal（NH₄）_0.33WO₃.F-doping promotes the growth of ammonium tungsten bronze from nanoparticles to rod-like materials,and preferred orientation along（100）direction.After F doping,the near infrared absorption of ammonium tungsten bronze increased significantly,the electron hole recombination rate decreased,and the electrochemical impedance decreased.（2）The effect of F doping on the photocatalytic activity of ammonium tungsten bronze was investigated under ultraviolet,visible and near infrared light.With the increase of molar ratio of fluorine to tungsten,the near infrared photocatalytic degradation rate of fluorine-doped ammonium tungsten bronze increased from 20%to 83%.When the molar ratio of fluorine to tungsten is 11.2:1 and the molar ratio of ammonium to tungsten is 1:1,the reaction constant is 0.0102 min^-1,which is 8.4 times that of tungsten bronze without fluoride.The photocatalytic degradation rate of ultraviolet light increased from 19%to 36%,and that of visible light increased from 39%to 76%.Therefore,fluorine-doped ammonium tungsten bronze nanorods have full spectrum photocatalytic activity.（3）F-doped（NH₄）_0.33WO₃/Pd composite was prepared by chemical reduction method.The effects of different Pd loadings on the full-spectrum photocatalytic performance of fluorine-doped ammonium tungsten bronze were investigated.The UV,visible and near-infrared photocatalytic activity of F-doped（NH₄）_0.33WO₃/Pd composites increased and then decreased with the increase of Pd loading.When the theoretical mass ratio of fluorine-doped ammonium tungsten bronze to metal Pd is 15:1,the composite has the highest photocatalytic activity.The degradation rates of Rhodamine B solution under ultraviolet,visible and near-infrared light were 76%,86%and 91%,respectively.