Photocatalytic Properties Of Hollow Ta₂O₅/TiO₂ Prepared By The Controllable Oxidation Of TaTiC₂/C

With the problems of resources and environment becoming more and more serious,the research and application of photocatalytic materials in the field of solar energy conversion and environmental pollution treatment and other aspects provides the ideal solution for these two problems:energy crisis and environmental pollution.Among the photocatalytic materials,TiO₂ attracts the most attention owing to its low cost,non-toxic,mild reaction conditions,and so on.Using titanium powder,tantalum powder and carbon black as raw materials,TaTiC₂/C were in-situ synthesized in KCl-LiCl molten salt medium.Then TaTiC₂/C was used as carbide precursor to prepare the hollow Ta₂O₅/TiO₂ composite photocatalyst by the controllable oxidation.In this work,the effects of molten salt reaction temperature,molten salt reaction time,n_C/n_M,n_Ti/n_Ta and oxidation temperature on the crystal phases of TaTiC₂/C and the corresponding oxidation products were studied.The as-prepared composite materials were characterized and analyzed by XRD,SEM,TEM,DRS and other techniques.The photocatalytic activities of hollow Ta₂O₅/TiO₂ composite photocatalysts were evaluated by using 10 mg/L methylene blue solution as the target pollution and ultraviolet light as light source.The main conclusions were summarized as following:1 It is feasible and effective to control the composition and structures of TaTiC₂/C by the molten salt method.Appropriately increasing the reaction temperature,prolonging the reaction time and decreasing the n _C/n_M are beneficial to the crystal growth of TiTaC₂.TaTiC₂/C synthesized by molten salt reaction at a temperature of 1030 ^oC for 4h maintains the spherical shape of carbon black.When n_C:n_Ti:n_Ta is 6:2.5:1.5,TaTiC₂ coating is uniform and compact,closely bounding with carbon black,and its thickness is about 30 nm.2 The composite photocatalysts Ta₂O₅/TiO₂ with hollow spherical shell structure were prepared by the controllable oxidation using Ta TiC_2/C as precursors.Ta₂O₅ and TiO₂ are uniformly mixed and distributed with nanometer particle size.The pores in the sample are mainly mesoporous and macroporous.The shortcomings of poor adsorption for organic pollutants by TiO₂ photocatalyst and heterogeneous composite of traditional composite methods are solved.3 Oxidation temperature can greatly affect the composition and photocatalytic properties of hollow Ta₂O₅/TiO₂ composite photocatalyst.The experimental results showed that the photocatalytic degradation rate of Ta₂O₅/TiO₂ was higher,when the TiO₂ phase coexisted with anatase and rutile?450?650°C?.Followed by amorphous?350°C?and rutile completely was the lowest?750?850°C?.4 The band gap of Ta₂O₅/TiO₂ composite photocatalysts are between TiO₂?2.84 eV?and Ta₂O₅?3.87 eV?,and the coupling of the band structure suppresses the recombination of carriers.The photocatalytic activities of Ta₂O₅/TiO₂ composite photocatalysts were significantly higher than that of single Ta₂O₅ or TiO₂.When n_C:n_Ti:n _Ta=6:2.5:1.5 was used,the photocatalytic degradation rate was as high as 97%.