| Photocatalytic technology has an attractive prospect in environmental wastewater treatment.TiO2 is the most important photocatalyst because of its excellent photocatalytic properties,strong oxidizing property,stable chemical property,low cost and non-toxicity.However,it is limited because electron-hole pairs are easy to combination and effective quantum yield is low.In this paper,by recombining TiO2 and graphene,compositing with YFeO3 to form a p-n junction to enhance the catalyst adsorption of organic pollutants,inhibit its photogenerated electron-hole pairs,expand the spectral response range,and ultimately increase the photocatalytic activity of the catalyst.The main research contents are as follows:With graphite powder as raw material,the Hummers and improved Hummers methods were adopted,respectively,to prepare graphite oxide.And then graphene oxide(GO)was obtained by ultrasonic dispersion.By characterization of XRD,the interplanar spacing of GO has become lager because of the insertion of oxygen containing functional groups.At the same time,by comparing the infrared spectrogram of samples prepared by Hummers and improved Hummers methods,we could know that compound material prepared by simplified experimental process-improved Hummers method,can also be successfully oxidized.The samples containing functional groups like-COOH,-OH,C=O,etc.The introduction of oxygen containing functional groups enhanced the hydrophilicity of graphite oxide,so that it can be evenly dispersed in water.Moreover,the functional groups provide active sites for YFeO3/TiO2 composites to grow on the graphene substrateYFeO3 powder in different crystal forms was prepared using the sol-gel method.The products were characterized by X-ray diffraction(XRD),differential thermal analysis-thermogravimetric analysis(DTA-TG),special surface area analysis(the BET method),and ultraviolet-visible diffuse reflectancespectroscopy(UV-Vis DRS).The photocatalytic activities of the samples were evaluated using the photocatalytic degradation of methylene blue under visible light.The result was that when the temperature increased from 973 K to 1073 K,the crystal form of YFeO3 was changed from hexagonal to orthorhombic phase.Compared to orthorhombic phase,the hexagonal phase presented relatively larger specific surface area,wider absorption edge,a narrower bandgap width,a more negative valence position,and a more positive conduction band position.At the same time,the result of photocatalytic degradation of methylene blue was better.YFeO3/TiO2 composites(YT)were prepared by physical combination of YFeO3 and TiO2 powders,and investigate the suitable experimental parameters by changing the ratio of YFeO3 in YFeO3/TiO2 composites.Meanwhile,pure TiO2 powder was used as the blank under the same experimental conditions.The products were characterized by scanning electron microscope(SEM),special surface area analysis(the BET method)and ultraviolet-visible diffuse reflectance spectroscopy(UV-Vis DRS),the results show that with the ratio of YFeO3 in YFeO3/TiO2 composites increasing,the specific surface area of the composites decrease and the bandgap width increase gradually.The composite YT-2.5 has the best combination effect and the degradation rate of MB was 56%under visible light irradiation.A series of three-phase composite samples were prepared by changing the hydrothermal temperature of graphene and YFeO3/TiO2 composites,while other conditions unchanged.Compared with pure YFeO3 podwers and YFeO3/TiO2 composites,the three-phase composites photocatalyst have higher degradation rate and better degradation effect under visible light.The sample GYT-140,prepared at hydrothermal reaction temperature of 413 k,has stronger adsorption capacity,which promotes the catalytic degradation of MB under visible light and makes the degradation rate of MB in visible light from YFeO3/TiO2 composites 56%of the material increased to 73%of the three-phase composite GYT-140. |
PDF Full Text Request