| Bismuth tungstate(Bi2WO6)has suitable band gap width and special layered structure,which has great potential in the treatment of organic pollutants.However,low visible light utilization and recombination of photogenerated carriers inhibit its photocatalytic activity.At present,researchers mainly focus on the improvement of light absorption range and carriers migration,so as to improve the photocatalytic effect.In order to improve the photocatalytic performance,the composite materials with reasonable band structure should be constructed.Based on the basic researches,modification of Bi2WO6 was studied in this paper.Using bismuth nitrate and ammonium tungstate as bismuth source and tungsten source respectively,Bi2WO6 powders with stable structure were prepared by sol-gel method.Ag loaded Bi2WO6 composite materials were successfully prepared by photoreduction method.Bi2WO6-SiO2 composite powders with porous structure were synthesized by impregnation method using SiO2 inverse opal photonic crystal as structural framework.The photocatalytic materials of g-C3N4-Bi2WO6 were prepared by in situ calcination.The composition,morphology,structure and fluorescence intensity of photocatalysts were analyzed by means of X-ray diffraction,scanning electron microscope,Fourier infrared and fluorescence.The photocatalytic performance of prepared samples were tested by degradating Rhodamine B(RhB)in water under visible light,and the mechanism of photocatalytic degradation was explored by capture experiments.The effects of different technological factors on photocatalytic performance of Ag-Bi2WO6,Bi2WO6-SiO2 and g-C3N4-Bi2WO6 were studied.The main results are as follows:(1)Bi2WO6 powders are successfully synthesized by sol-gel method,and Ag-Bi2WO6 composites are obtained by photoreduction.When the concentration of AgNO3 solution is 0.01 mol/L and the volume is 3 mL,the photocatalytic activity of Ag-Bi2WO6 composite is 0.82 times higher than that of pure Bi2WO6.On the one hand,the improvement of photocatalytic performance is due to the formation of heterogeneous interface between Ag and Bi2WO6,which effectively improves the separation of photogenerated carriers.On the other hand,due to the surface plasmon resonance effect of Ag particles,the electrons generated by photo excitation can be transferred to the surface of the catalyst and combined with adsorbed O2 to produce O2-with strong oxidation ability,which greatly improves the photocatalytic performance.(2)Bi2WO6-SiO2 composite powders with good adsorption and photocatalytic property are synthesized by impregnating Bi2WO6 precursor solution into inverse opal structure SiO2 framework.The effects of impregnation time,calcination temperature and holding time on the photocatalytic properties of the materials were studied.When the impregnation time is 10 min and calcined at 750℃ for 4 h,the sample with best photocatalytic performance is obtained.The degradation rate of RhB is 99.43%under visible light irradiation for 120 min.SiO2 inverse opal photonic crystal can reduce the agglomeration of Bi2WO6,expand the specific surface area,and improve the adsorption of pollutants.At the same time,the slow photon effect and photon localization effect of inverse opal photonic crystal effectively improve the visible light utilization efficiency of Bi2WO6,thus improving the photocatalytic performance.(3)Firstly,g-C3N4 is prepared by high temperature condensation method,and then g-C3N4-Bi2WO6 heterogeneous photocatalytic materials are prepared by simple in-situ calcination method.When the addition amount of g-C3N4 is 0.08 g,g-C3N4-Bi2WO6 photocatalyst calcine at 300℃ for 1 h had the highest degradation rate of RhB,and the degradation rate reach 98.1%under visible light irradiation for 120 min.The main reason for the improvement of photocatalytic performance of the composite is that the direct Z-type heterostructure formed by g-C3N4-Bi2WO6 and Bi2WO6,which effectively improves the redox ability of the composite. |
PDF Full Text Request