Study On Soft-chemical Synthesis And Properties Of Bismuth Vanadium(Molybdate) Photocatalyst

Since 21 st century,human beings are facing the energy crisis,environment was worsening day by day,so make full use of natural resources has become the main research direction.Solar energy was the most abundant natural resources,and photocatalytic degradation of organic pollutants just can make full use of solar energy.In recent years,the research of photocatalysis technology had become a hot spot,the development of new semiconductor photocatalyst had great significance to the efficient use of solar energy.Bismuth（bismuth）molybdate was a representative of the bismuth photocatalyst,which not only had good visible photocatalytic activity,but also cause no secondary pollution.It attracted the attention of researchers at home and abroad.In this paper,focus on explore the optimum pH in synthesis of bismuth vanadate by ethylene glycol solvothermal method,and on the basis of optimum pH doped Cu;and then studied the optimum calcination temperature in synthesis of bismuth molybdate by sol-gel method.Then co-doped with metal（Eu and Fe）in crystalline to improve the visible light photocatalytic activity of bismuth molybdate under the optimum calcination temperature.The following is a specific study:（1）Bismuth vanadate was prepared by ethylene glycol solvothermal method（reaction time was 10 h,reaction temperature wad 180 ℃）used Bi（NO3）3·5H2O and NH4VO3 as raw materials.Effects of different pH on the photocatalytic activity to degradation of Rhodamine B of the bismuth vanadate were studied.Structure,morphology,chemical valence and properties of optical absorption of the as prepared bismuth vanadate were characterized by SEM,XRD,XPS and UV-Vis DRS.The results showed the photocatalytic activity of sample pH at 11 is highest and the degradation rate of Rhodamine B in 50 min is about 37.06%.Then on the basis of optimum pH,a series of cocoon-like hierarchical structures xCu-BiVO₄ photocatalysts were successfully synthesized by ethylene glycol solvothermal method with ethylene diamine tetraacetic acid（EDTA）as the chelating agent.The as-prepared samples were characterized by XRD,XPS,SEM,BET,UV-Vis DRS and PL,respectively.It was shown that the amount of Cu²⁺has no effect on the crystal phases of BiVO₄ but plays an important role on the morphology,the catalysts turned from flower-like into cocoon-like hierarchical structures due to Cu²⁺ doping.Results showed that Cu²⁺ doping can effectively enhance the photocatalytic activities of the BiVO₄ which were evaluated by the degradation of RhB under visible-light irradiation.The improvement of photocatalytic activity is due to the changed morphology,the enhancement of light absorption,the narrow band gap and the low recombination ratio of photo-induced electron-hole pairs.The best photocatalytic performance is obtained for 1.5Cu-BiVO₄,of which the RhB photo-degradation rate can reach to be 96% after 50 min under visible-light irradiation.（2）Bismuth molybdate was prepared by citric acid sol-gel process used ammonium molybdate and bismuth nitrate as raw materials.Effects of different calcination temperature on the photocatalytic activity to degradation of RhB of the bismuth molybdate were studied.Structure,morphology,chemical valence and properties of optical absorption of the as prepared bismuth molybdate were characterized by means of SEM,XRD,TEM,XPS and UV-Vis DRS.The results showed the photocatalytic activity of sample calcinated at 450 ℃is highest and the degradation rate of RhB in 50 min is about 58%.Then on the basis of optimum calcination temperature,the BMO,Eu-BMO,Fe-BMO and Eu-Fe-BMO co-doping honeycomb-like Bi₂Mo₃O₁₂ nanoparticles have been prepared through a citric acid complex process.The samples were characterized using XRD,XPS,SEM,UV-vis and PL and their photocatalytic activities have been investigated by the photocatalytic degardationn of RhB.The structural analysis indicates that all samples are α-Bi₂Mo₃O₁₂ phase.It was found that Eu-Fe-BMO exhibited the highest activity with the degradation rate of RhB be 94.1% in 50 min because the doped Eu3+ and Fe3+ ions inhibit the recombination of electrons and holes.But the photocatalytic performance of Eu-Fe-BMO was not simply the sum of Eu-BMO and Fe-BMO two individual catalysts due to the certain doped capacity at most in Bi₂Mo₃O₁₂.